Flat rubber washers are the workhorse seal: a flat ring of rubber that compresses between two surfaces to block water, dampen vibration, insulate electrically, or protect finishes from metal hardware. Rubber Washer Warehouse stocks flat rubber washers in every OD, ID and thickness combination — over 1,700 sizes — in seven materials, sold individually and in bulk.
What flat rubber washers are used for
Sealing: faucets, hose connections, tank fittings, enclosure penetrations — anywhere a fastener or coupling passes liquid. Vibration damping: under motor mounts, appliances, pumps and fan housings. Surface protection: between metal hardware and glass, tile, fiberglass, or painted panels. Spacing and insulation: electrical standoffs and anti-galvanic barriers between dissimilar metals.
Pick your material
| Material | Temp range | Strongest against | Typical use |
|---|---|---|---|
| EPDM | −40°F to 257°F | Water, UV, ozone, chlorine | Plumbing, outdoor, roofing |
| Neoprene | −40°F to 212°F | Weather + moderate oil | General purpose, marine, HVAC |
| Nitrile | −40°F to 257°F | Oil, fuel, grease | Automotive, hydraulics |
| Silicone | −85°F to 400°F | Extreme heat & cold, food contact | Appliances, food equipment |
| Viton | −15°F to 400°F | Aggressive chemicals & fuels | Chemical processing |
| Natural rubber | −40°F to 180°F | Abrasion, rebound | Vibration, impact |
| Fiber | to 250°F | Rigid spacing, insulation | Electrical, drain plugs |
Not sure which? The material comparison guide puts them side by side.
How flat washer sizes work
Three numbers define every flat washer: OD (outer diameter), ID (inner diameter — matches your bolt or fitting), and thickness. We stock ODs from 1/4" up to 4", IDs down to 1/8", and thicknesses from 1/16" to 1/2". Grab calipers and follow the measuring guide, then jump straight to your size from the complete size chart. Small flat rubber washers (under 1/2" OD) for electronics and instruments, and large flat rubber washers (2"–4" OD) for tank fittings and flanges, ship from the same stock.
Thin vs thick flat washers
Thin washers (1/16"–3/32") seal machined, flat surfaces with minimal stack height. Standard 1/8" suits most plumbing and fastening work. Thick washers (1/4"–1/2") absorb vibration, bridge rough or uneven surfaces, and take up slack in oversized holes — they compress more, so leave torque margin.
FAQ
What's the difference between a flat rubber washer and a gasket?
Shape and scope: washers are standardized rings that seal around a fastener or fitting; gaskets are cut to match a whole mating surface. Our washer vs gasket guide covers when each applies.
Can I stack flat rubber washers?
For sealing, one correctly sized washer beats a stack — stacked rubber squirms sideways under load. For spacing or vibration, stacking two is fine.
Do you sell flat rubber washers in bulk?
Yes — every size has automatic volume pricing, and the bulk & wholesale program covers larger runs. Contact us for pallet quantities or custom sizes.