Custom Rubber Seal Manufacturer: RFQ Checklist

Why a Complete RFQ Matters for Custom Rubber Seals

[2026-09-06] | By Xiamen Jinshun Sealing Technology Co., Ltd.  Annie Xu   ywb6@jinshunxm.com

A complete rubber seal RFQ should define the part geometry, elastomer, hardness, operating temperature, pressure, sealing medium, movement, tolerances, certification requirements, quantity and commercial requirements. These specifications determine whether a manufacturer can select an appropriate compound, manufacturing process, tooling strategy and inspection plan before quoting.

For a custom rubber seal, a drawing alone may not be enough. Two seals with identical dimensions can require different compounds or designs if one is exposed to hot water and the other to lubricating oil, or if one is static while the other operates under reciprocating motion.

For buyers evaluating a custom rubber seal manufacturer, a useful RFQ should therefore answer five questions:

• What is the part?
• What environment will it operate in?
• What performance is required?
• What regulatory or quality requirements apply?
• How will the parts be manufactured, inspected and supplied?

The more complete these inputs are, the less likely the quotation process is to depend on assumptions.

The first RFQ requirement is a clear definition of the part itself.

Ideally, provide a 2D engineering drawing showing critical dimensions and tolerances together with a 3D CAD model when the geometry is complex. If a drawing is unavailable, a physical sample can help a manufacturer evaluate the existing component and develop a quotation.

The RFQ should identify:

• Part number
• Drawing revision
• 2D drawing
• 3D CAD model, if available
• Physical sample, if available
• Critical sealing dimensions
• Assembly location
• Functional requirements
• Existing failure issues, if applicable

A physical sample can be particularly useful when replacing an existing rubber component but does not have to be treated as a complete specification. Material identification, dimensional verification and application requirements may still need to be confirmed.

For custom rubber parts, the manufacturer should distinguish between dimensions that define the sealing function and dimensions that are less critical to assembly.

For O-rings and other circular sealing components, dimensional information is fundamental to tooling, gland fit and compression.

For an O-ring, buyers should normally identify:

• Inside diameter (ID)
• Outside diameter (OD)
• Cross-section (CS)
• Dimensional tolerances
• Groove dimensions, when available
• Installed condition

For molded gaskets and other non-circular components, provide the complete profile and critical sealing dimensions rather than relying on overall length and width alone.

The relationship between seal dimensions and the mating groove determines squeeze, stretch, clearance and installation conditions. A manufacturer should not select dimensions only from the nominal part size without considering the actual gland design.

If the seal is replacing an existing component, provide the mating-part information where possible.

Dimensional information to include in an RFQ

If any dimensional requirement is unknown, the specification should be confirmed according to the actual application and drawing.

Material selection should be based on the operating environment rather than the elastomer name alone.

Common rubber and silicone materials used for custom sealing applications include NBR, EPDM, silicone and FKM. Their suitability depends on temperature, sealing medium, pressure, movement, compression, chemical exposure, service-life requirements and regulatory requirements.

This table is a selection framework, not a blanket material recommendation. Compound formulation can materially affect performance within the same elastomer family.

For example, an EPDM seal intended for a water-treatment application should be evaluated against the actual water chemistry, temperature, pressure, compression and applicable certification requirements.

The RFQ should specify the required material family or allow the manufacturer to recommend one based on documented application conditions.

Custom Sealing Solutions can be used when requesting a custom sealing component based on application requirements.

Shore A hardness should be specified when the application requires a defined hardness range.

Hardness affects how an elastomer responds to compression, deformation, installation and contact with mating surfaces. However, selecting a seal based only on hardness is not sufficient.

A harder compound is not automatically better for every application, and a softer compound is not automatically better at preventing leakage.

The RFQ should identify:

• Target Shore A hardness
• Permitted tolerance or range
• Test method where applicable
• Whether hardness is a critical characteristic

Hardness should be evaluated together with compression set, tensile properties, elongation, tear strength, temperature, pressure, media compatibility and seal geometry.

If the buyer does not have a defined hardness requirement, the specification should be confirmed according to the actual application and drawing.

Temperature is one of the first environmental conditions a rubber seal manufacturer should evaluate.

Do not provide only a single maximum temperature if the seal experiences a variable operating cycle. Where possible, provide:

• Normal operating temperature
• Minimum temperature
• Maximum temperature
• Continuous exposure temperature
• Short-duration peak temperature
• Heating and cooling cycles
• Cleaning or sterilization conditions, where applicable

Temperature affects elastomer behavior, compression set, aging and dimensional stability. The compound should therefore be selected according to the actual temperature profile rather than a generic material temperature range.

For equipment exposed to hot water, steam, oil or other heated media, describe the actual operating conditions in the RFQ.

Pressure should be stated together with seal geometry and application type.

Provide:

• Normal working pressure
• Maximum working pressure
• Pressure fluctuations
• Pressure spikes, if known
• Static or dynamic pressure condition
• Mating clearance
• Seal orientation

Pressure does not act independently of the seal design. Extrusion risk, gland geometry, clearance gap, elastomer hardness and backup arrangements can all affect sealing behavior.

For hydraulic or pneumatic applications, the RFQ should also identify whether the seal is exposed to reciprocating, rotary or stationary movement.

For pressure-sensitive applications, the manufacturer may need additional gland and mating-component information before confirming the final specification.

Request a Seal Engineering Review

The sealing medium should never be omitted from a technical rubber seal RFQ.

State exactly what contacts the elastomer, such as:

• Water
• Hot water
• Air
• Hydraulic fluid
• Lubricating oil
• Fuel
• Cleaning chemicals
• Process chemicals
• Food or beverage
• Other application-specific fluids

Where relevant, provide the fluid's concentration, additives, pH, cleaning regime and exposure duration.

The same elastomer family can perform differently depending on compound formulation and exposure conditions. A material that works in one fluid may not be suitable for another.

For drinking-water applications, buyers should identify the intended market and applicable regulatory requirements. Certification availability depends on the material, product and application.

Relevant requirements may include FDA, NSF, WRAS, ACS, KTW-W270 or LFGB, depending on the specific product and market. These should be verified for the exact material and finished component rather than assumed from the elastomer family.

Jinshun's product scope includes RO membrane seals, water-contact sealing components and silicone tubing, making the sealing medium particularly important for water-treatment RFQs.

Tell the manufacturer whether the seal remains stationary or moves during operation.

The main application categories include:

A seal designed for a static application should not automatically be transferred to a dynamic application without reviewing the design.

For dynamic seals, provide shaft speed or movement information where applicable, along with pressure, temperature, lubrication and surface conditions.

This information helps the manufacturer evaluate whether an O-ring, V-seal, oil seal or another sealing configuration is more appropriate.

Jinshun supplies O-rings, V-seals, oil seals and custom rubber components for different sealing requirements.

A rubber seal drawing should distinguish between nominal dimensions and required tolerances.

Not every dimension needs the same tolerance. Critical sealing dimensions should be identified so the manufacturer can evaluate mold capability, process variation and inspection requirements.

The RFQ should identify:

• Critical dimensions
• General dimensional tolerances
• Functional tolerances
• Rubber material tolerance requirements
• Flash limits where applicable
• Parting-line requirements
• Visual acceptance criteria

For molded parts, tooling design and process selection influence achievable dimensional consistency.

If the part has a tight tolerance requirement, the buyer should identify it before tooling is developed rather than after samples have been produced.

The specification should be confirmed according to the actual application and drawing where the required tolerance is not known.

Certification requirements should be tied to the final application and destination market.

Possible requirements may include:

• ISO 9001
• ISO 14001
• RoHS
• REACH
• PAHS
• FDA
• NSF
• WRAS
• ACS
• KTW-W270
• LFGB
• UL

Not every rubber seal requires every certification.

For example, a drinking-water component may require a specific water-contact approval, while an industrial component may instead require material documentation, dimensional inspection or application-specific testing.

An RFQ should therefore specify:

• Destination market
• Application
• Required certification
• Required material documentation
• Test report requirements
• Traceability requirements
• Customer audit requirements, if applicable
• Certification availability depends on the material, product and application.

Quantity affects the manufacturing and tooling decision.

Provide:

• Prototype quantity
• Initial order quantity
• Annual demand
• Forecast volume
• Expected order frequency
• Required MOQ
• Packaging quantity

A low-volume custom seal and a high-volume OEM component may require different tooling and production approaches.

The relationship is:

Part geometry → material → volume → tooling → process → tolerance → cost

For high-volume molded components, dedicated tooling may be commercially justified. For prototypes or low-volume applications, the tooling and production strategy may be different.

An experienced custom rubber parts manufacturer should evaluate the projected volume before finalizing the manufacturing process.

Color and packaging requirements should be included before mass production.

Specify:

• Rubber color
• Pantone or approved color reference where required
• Surface appearance
• Individual packaging
• Bulk packaging
• Label requirements
• Part number
• Batch number
• Country-of-origin marking
• Private-label requirements
• Carton requirements

Color should not be treated only as a cosmetic specification when it is used to distinguish materials, versions or product families.

For private-label and distributor programs, packaging and labeling requirements should be agreed during the quotation stage.

Custom Sealing Solutions

Before production tooling is released, the buyer and manufacturer should agree on the prototype process, tooling ownership and approval procedure.

The RFQ should clarify:

• Prototype quantity
• Prototype material
• Prototype manufacturing method
• Production material
• Tooling requirement
• Tooling ownership
• Mold revision control
• Sample approval procedure
• Production approval criteria

For molded rubber products, tooling cost is influenced by factors such as part geometry, cavity configuration, material, expected production volume, tolerance requirements and manufacturing process.

Compression molding, injection molding and transfer molding can be considered according to the component geometry, material and production requirements. Extrusion may be appropriate for continuous rubber profiles or tubing.

For silicone components, liquid silicone rubber processing may also be considered where applicable.

Tooling should be evaluated as part of the overall manufacturing plan rather than as an isolated purchase.

Jinshun Manufacturing Capability provides the appropriate reference point for buyers evaluating manufacturing and tooling requirements.

Send Your Seal Drawing

A procurement-ready RFQ does not need to be complicated. It needs to remove the assumptions that can change material selection, tooling, production cost or performance.

A practical RFQ could contain the following information:

A useful RFQ should also identify known problems with the existing seal. For example, tell the manufacturer if the current part experiences leakage, compression-set issues, cracking, swelling, extrusion, wear or installation damage.

That information can be more valuable than simply requesting a lower unit price.

Once the RFQ has been reviewed, the manufacturer should translate the application requirements into a practical production specification.

Depending on the product, this may include:

• Material and compound identification
• Mold design
• Cavity configuration
• Manufacturing process
• Post-curing requirements where applicable
• Dimensional inspection
• Hardness testing
• Visual inspection
• Flash and parting-line inspection
• Compression-set testing
• Tensile or elongation testing
• Aging testing
• Media-resistance testing
• Pressure testing
• Air-tightness testing

The exact inspection plan should match the application.

For example, a simple static gasket may require dimensional and visual inspection, while a pressure-containing fluid-control component may require additional pressure or leakage testing.

Material traceability and batch consistency should also be considered when the application has strict quality requirements.

Buyers should ask the supplier which inspection records can be provided with samples and production batches.

Before approving a custom rubber seal for mass production, verify that the approved sample matches the final production specification.

The review should cover:

• Correct material
• Correct hardness
• Correct dimensions
• Critical tolerances
• Surface appearance
• Flash and parting line
• Assembly fit
• Compression or squeeze
• Functional sealing
• Required testing
• Certification documentation
• Packaging
• Part identification
• Drawing revision

Do not approve a production sample solely because it visually resembles the reference sample.

For an OEM component, the production approval should be based on the agreed engineering specification and application requirements.

Water Treatment and Drinking Water Equipment

Specify the water type, temperature, pressure, contact duration and applicable drinking-water requirements.

Products such as RO membrane seals, filter seals, valve seals and silicone tubing may require different material and geometry considerations.

For regulated drinking-water applications, confirm the exact certification required for the destination market and finished product.

Bathroom and Sanitaryware

For faucet seals, shower gaskets, valve components and shower-related silicone parts, provide water temperature, pressure, assembly conditions and expected service environment.

If the component is in direct water contact, identify the applicable market and regulatory requirement.

Automotive

Automotive RFQs should identify the fluid, temperature cycle, pressure, vibration, movement and location of the seal.

Oil seals, O-rings, gaskets and molded rubber components may have substantially different operating requirements.

Industrial Machinery

For industrial equipment, identify whether the seal is hydraulic, pneumatic, rotary, reciprocating or static.

Pressure, fluid, speed, temperature, clearance and surface conditions are particularly important for dynamic sealing applications.

Food and Beverage Equipment

For food-contact components, identify the food or beverage medium, cleaning conditions, temperature and required regulatory documentation.

If FDA, LFGB or another requirement applies, specify the exact market and compliance requirement rather than simply requesting "food grade."

For buyers evaluating related sealing products, Jinshun's O-rings page can be used as a product reference when the application involves standard or custom O-ring components. O-Rings

For broader custom component requirements, use Custom Sealing Solutions to communicate the application, drawing and required specifications. Custom Sealing Solutions

The company's rubber parts information is also relevant when the RFQ involves molded rubber components rather than a conventional O-ring. Rubber Parts

Request a Custom Rubber Seal Quote

What information should I provide when requesting a custom rubber seal quote?

Provide the drawing or sample, dimensions, material, Shore A hardness, temperature, pressure, sealing medium, static or dynamic application, tolerances, certification requirements, quantity, packaging and tooling requirements. The specification should be confirmed according to the actual application and drawing.

How do I choose between EPDM, NBR, silicone and FKM?

Compare temperature, pressure, fluid compatibility, movement, compression, chemical exposure, aging, regulatory requirements and cost. No elastomer should be selected from a single property alone. The final compound should be verified against the actual application conditions.

What certifications are required for drinking-water rubber seals?

Requirements depend on the destination market, application, material and finished product. Potential references include NSF, WRAS, ACS and KTW-W270. Buyers should verify the exact certification required for the specific component rather than assuming that an elastomer is automatically compliant.

Can a China rubber seal manufacturer produce parts from a physical sample?

A manufacturer can use a physical sample as a reference for quotation and development, but the sample does not necessarily define all engineering requirements. Material, dimensions, tolerances and operating conditions should be confirmed before production tooling is finalized.

What affects the tooling cost of custom molded rubber parts?

Tooling cost can be affected by part geometry, cavity configuration, manufacturing process, material, tolerance requirements and expected production volume. Prototype requirements and tooling ownership should also be agreed before production tooling is commissioned.

A useful RFQ gives the manufacturer enough information to make an engineering-based quotation instead of a price based on assumptions.

Before contacting a supplier, prepare:

• Part drawing or physical sample
• ID, OD, cross-section or complete profile
• Material requirement
• Shore A hardness
• Operating temperature
• Working pressure
• Sealing medium
• Static or dynamic application
• Dimensional tolerances
• Certification and compliance requirements
• Prototype and annual quantity
• Packaging, branding and tooling requirements

For complex components, also provide the mating-part drawing, groove dimensions, known failure modes and required inspection documentation.

A qualified custom rubber seal manufacturer should then be able to evaluate the relationship between material, geometry, process, tooling, tolerance and application before confirming the production specification.

If you are sourcing custom O-rings, gaskets, oil seals, V-seals, RO membrane seals, silicone tubing or other molded rubber components, send the drawing or sample together with the operating conditions. The final specification should be confirmed according to the actual application and drawing.

Request a Custom Rubber Seal Quote