50pcs EPDM Black O-Rings Rubber Seals CS1/1.2mm OD 4–40mm

50-Pack EPDM Rubber O-Rings — Reliable Waterproof Sealing in Every Size

Keep leaks at bay with these high-quality EPDM O-Rings from Ouling. Each bag contains 50 pieces of precision-molded black rubber ring gaskets, available in a wide range of outer diameters (OD 4–40mm) with a cross-section (CS) of 1mm or 1.2mm. Whether you're working on plumbing, hydraulic systems, automotive applications, or general mechanical assemblies, these O-rings deliver consistent, durable sealing performance.

Made in Mainland China.

Key Features

• Material: Premium EPDM rubber — excellent resistance to water, weathering, and corrosion
• Temperature Range: Rated for use from -50°C to +150°C (-58°F to 302°F)
• Wear Resistant: Engineered to withstand repeated compression and friction cycles
• Waterproof & Corrosion Resistant: Creates a tight, reliable seal against moisture and mild chemicals
• Size Variety: OD 4mm to 40mm with CS 1mm / 1.2mm cross-section — covers most standard applications
• Color: Classic black for universal compatibility
• Shape: Standard ring gasket profile for drop-in replacement
• Quantity: 50 pieces per bag — great value for repairs, maintenance, and stock

Specifications

Common Applications

• Plumbing fixtures and pipe fittings
• Automotive fuel and cooling systems
• Hydraulic and pneumatic equipment
• Pumps, valves, and compressors
• Garden hose connectors and sprinkler systems
• Electronics enclosures requiring moisture sealing

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Learn more: OSHA on personal protective equipment

Frequently Asked Questions

Q: What does EPDM mean and why is it a good material for O-rings?

A: EPDM stands for Ethylene Propylene Diene Monomer — a synthetic rubber known for its outstanding resistance to water, steam, weathering, and ozone. EPDM O-rings maintain their flexibility and sealing integrity across a wide temperature range (-50°C to +150°C), making them an excellent choice for both indoor plumbing and outdoor or automotive applications.

Q: How do I choose the right O-ring size from this set?

A: Measure the groove or fitting where the O-ring will sit. You'll need the outer diameter (OD) — available from 4mm to 40mm in this set — and confirm the cross-section thickness (CS) matches your groove depth (1mm or 1.2mm options). When in doubt, consult your equipment's service manual or measure an existing O-ring with calipers for an exact match.

Q: Are these O-rings suitable for use with fuel or oil systems?

A: EPDM rubber is best suited for water, steam, mild chemicals, and outdoor weathering applications. It is not recommended for use with petroleum-based fluids, fuels, or oils. For fuel/oil applications, consider Nitrile (NBR) or Viton O-rings instead.

Q: Can I order custom sizes beyond the OD 4–40mm range?

A: Yes — custom sizes are available. Please contact us with your required specifications (inner diameter, outer diameter, and cross-section) and we'll be happy to assist with a custom order.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.