Custom Molded Silicone O-rings
Manufacturer & Custom Solutions
Custom Molded Silicone O-rings
When standard sizes do not fit, ZSR Silicone builds custom molded O-rings to your exact drawing. We work from CAD files or physical samples, machine the mold, and deliver prototypes in days. Materials include solid silicone, fluorosilicone, conductive grades and more.
FDA 21 CFR 177.2600
Rubber Articles Intended for Repeated Use
LFGB 30&31
EU Food Contact Materials
USP Class VI / ISO 10993
Biocompatibility of Medical Devices
RoHS / REACH
Environmental Compliance
UL 94
Flammability of Plastic Materials
Built to Your Exact Spec
Custom Silicone O-ring Options
| Image | Product | Type | Short Info | Action |
|---|---|---|---|---|
 | ISO 3601 Metric Silicone O-Rings | Standard & Size | Metric silicone O-rings manufactured to ISO 3601 dimensions. Fits international equipment groove standards. | View Details |
 | ISO 6149 Metric Silicone O-Rings | Standard & Size | Metric O-rings designed for hydraulic and pneumatic fluid power sealing applications under ISO 6149 standards. | View Details |
 | BS 1806 Silicone O-rings | Standard & Size | British Standard inch-size silicone O-rings. Common in UK and Commonwealth industrial equipment. | View Details |
 | DIN 3771 Silicone O-rings | Standard & Size | German metric standard O-rings for hydraulic and pneumatic sealing in European machinery. | View Details |
 | Custom Molded Silicone O-rings | Standard & Size | Custom-shaped silicone O-rings molded to your exact drawing or sample. No standard size limitations. | View Details |
 | AS568 Silicone O-rings | Standard & Size | Inch-size silicone O-rings that follow the AS568 standard. Widely used in North American machinery and hydraulic systems. | View Details |
 | AN6227 Silicone O-rings | Standard & Size | Aerospace-standard O-rings with small cross-section. Used in aviation and military-grade sealing. | View Details |
 | AN6230 Silicone O-rings | Standard & Size | Aerospace-standard O-rings specified under AN6230 for aviation and military-grade sealing. | View Details |
 | JIS B2401 Silicone O-Ring | Standard & Size | Japanese industrial standard O-rings commonly used in Asian-manufactured machinery and automotive equipment. | View Details |
 | FDA Food Grade Silicone O-Rings | Grade | Food-safe silicone O-rings compliant with FDA regulations. Safe for repeated food contact. | View Details |
 | Industrial Grade Silicone O-ring | Grade | General-purpose silicone O-rings for industrial sealing. Cost-effective with reliable performance. | View Details |
 | Medical Grade Silicone O-ring | Grade | Biocompatible silicone O-rings for medical devices. Passes USP Class VI and supports sterilization. | View Details |
 | Oil-Resistant / Fuel-Resistant Silicone O-Rings | Special Function | Modified silicone O-rings that resist swelling in oils, fuels and petroleum-based fluids. | View Details |
 | Metal Detectable Silicone O-Rings | Special Function | Food-safe silicone O-rings with metal-detectable additives. Protects production lines from contamination. | View Details |
 | High Temperature / Heat Resistant Silicone O-Rings | Special Function | Silicone O-rings that stay flexible at temperatures above 200°C. For ovens, engines and furnaces. | View Details |
 | VMQ Silicone O-Rings | Materials | Heat and cold-resistant silicone O-rings for food, medical, automotive, and industrial applications. | View Details |
 | Fiberglass Reinforced Silicone O-rings | Materials | High-strength silicone O-rings reinforced with fiberglass fabric. Withstands extreme heat and pressure. | View Details |
 | HCR / HTV / Solid Silicone Rubber O-rings | Materials | Durable solid silicone rubber O-rings made by compression molding. The standard choice for general sealing. | View Details |
 | Liquid Silicone Rubber (LSR) O-rings | Materials | Injection-molded liquid silicone rubber O-rings with tight tolerances and clean surfaces. Ideal for high-volume production. | View Details |
 | Platinum Cured Silicone O-rings | Materials | Ultra-clean silicone O-rings cured with platinum catalyst. Lower extractables for food and medical use. | View Details |
 | Fluorosilicone (FVMQ) O-rings | Materials | Fuel and oil-resistant silicone O-rings for aerospace, automotive and chemical applications. | View Details |
 | Transparent / Clear Silicone O-rings | Color | See-through silicone O-rings for visual inspection and clean-looking medical or food equipment. | View Details |
 | Black / White Silicone O-Rings | Color | Standard black and white silicone O-rings. The most common colors for industrial and food-grade applications. | View Details |
 | Pantone Colors Silicone O-rings | Color | Silicone O-rings in any Pantone color for branding, color-coding or aesthetic requirements. | View Details |
 | Custom Colors Silicone O-rings | Color | Silicone O-rings matched to your exact color sample or specification. | View Details |
Custom Molded vs Standard O-Rings: What's the Difference?
Comparison Point | Standard O-Rings (AS568 / ISO 3601) | Custom Molded Silicone O-Rings | |
|---|---|---|---|
Size | Fixed standard sizes only | Any inner diameter and cross-section | |
Shape | Round cross-section only | Round, square, D-shaped, X-ring, lip seal, or any custom profile | |
Groove Fit | Buyer must design groove around standard size | O-ring is designed to fit the existing groove or housing | |
Minimum Order | Low — can buy 100 pieces | Higher — usually 1,000+ pieces to justify tooling | |
Tooling Cost | None — uses existing molds | One-time mold cost (ZSR keeps mold for future orders) | |
Lead Time | Fast — stock available | 2–4 weeks including mold making and sampling |
Key Message at ZSR:
If your equipment has a non-standard groove, if you need a special cross-section for better sealing, or if you cannot find a standard size that fits, custom molded is the right path. ZSR's engineering team can review your housing design and recommend the optimal O-ring geometry.
ZSR Custom Molding Capabilities
Suggested Sub-Points:
Mold Manufacturing
ZSR operates in-house CNC mold machining. We cut molds from high-grade tool steel or aluminum depending on your volume needs and budget.
Shape Flexibility
Beyond round O-rings, ZSR can mold square rings, D-rings, X-rings (quad rings), U-cups, V-rings, and complex multi-lobe profiles.
Surface Finish
Mold surfaces can be polished to SPI A-2 or SPI A-3 for clean, smooth parts with minimal flash.
Size Range
Custom molded silicone O-rings from 3 mm inner diameter up to 600 mm outer diameter. Cross-sections from 0.5 mm to 25 mm.
Material Options
All ZSR silicone grades available in custom molded form — industrial, FDA food grade, medical grade, high-temp, platinum cured, LSR, or HCR.
Hardness Range
10 to 90 Shore A, matched to your compression and sealing requirements.
Tolerance Control
Standard tolerances follow ISO 3601-3 Grade N or Grade S. Tighter tolerances available for precision applications upon request.
When to Choose Custom Molded Silicone O-Rings
Choose Custom Molded When:
You have a legacy machine
with a worn or obsolete seal that no standard size replaces.
Your groove is non-standard
for example, a rectangular channel, a dovetail slot, or a face-seal groove where a round ring does not seat properly.
You need a special cross-section
such as a square ring for better stability, an X-ring for lower friction, or a lip profile for directional sealing.
You are prototyping a new product
and need a small batch of seals for testing before committing to high-volume tooling.
You need overmolding
silicone molded directly onto a metal or plastic insert as one assembly.
Your equipment is imported
and uses a manufacturer-specific seal size not covered by AS568 or ISO 3601.
Do Not Choose Custom Molded When:
When to Choose Custom Molded Silicone O-Rings
Suggested List:
Key Message at ZSR:
If you can draw it, we can most likely mold it. Send ZSR your profile sketch and we will confirm feasibility within 24 hours.
What Is Custom Molded Silicone?
Custom molded silicone is silicone rubber that is shaped in a mold made specifically for your part. Unlike standard O-rings that come from fixed size tables like AS568 or ISO 3601, custom molded parts are made to fit your exact dimensions, groove shape, and performance needs.
How It Differs from Standard O-Rings
A standard O-ring is a simple circle with a round cross-section. It comes in set sizes that engineers around the world use in new designs. A custom molded silicone part can be any shape you need — round, square, D-shaped, or something completely unique. It is made for your equipment, not for a general catalog.
At ZSR Silicone Parts, we think of it this way: standard O-rings are like buying shoes in standard sizes. Custom molded parts are like having shoes made to measure. If your groove is unusual, if your old seal is obsolete, or if a standard ring simply does not fit, custom molding is the answer.
How ZSR Makes Custom Molded Silicone
The process starts with a mold. At ZSR, we machine the mold in-house using CNC equipment. The mold is a metal block with a cavity cut into it in the exact shape of your part. We place uncured silicone into the cavity, close the mold, apply heat and pressure, and the silicone cures into the finished shape.
Because we make the mold ourselves, we control the quality from the first step to the last. We can adjust the mold design if your part needs tighter tolerances, a smoother surface, or a special cross-section.
Why You Need Custom Molded Silicone
You need custom molded silicone when:
Custom molded silicone is simply silicone rubber made to your exact shape instead of a standard catalog size. It gives you the freedom to design seals that fit your equipment perfectly, not the other way around. At ZSR, we combine in-house mold making with full material flexibility to turn your drawing or sample into a finished, tested, production-ready seal.