Rubber O-Rings – Round Rubber Seals for Plumbing, Machinery & Marine (All Sizes)

Shop rubber O-rings — round-section O-ring seals that compress in a groove or against a fitting face to block water, air, and fluids. O-rings and seals are the simplest reliable sealing technology made: pick the right inside diameter and cross-section thickness, seat it clean, and it seals for years. Common uses include plumbing fittings and faucet repair, pump and filter housings, hydraulic and pneumatic fittings, marine hardware, and machinery service kits.

How to size an O-ring seal: match the inside diameter (ID) to the shaft or groove it stretches over, and the cross-section (thickness) to the groove depth — an O-ring should compress roughly 20-30% to seal. Measuring a worn ring? Measure ID and thickness with calipers, not the stretched-out old ring's appearance.

O-ring vs washer: a round-section O-ring seals in grooves and around shafts; a flat rubber washer seals under a fastener head or between flat faces. Full comparison in using rubber washers as gaskets, seals, and O-rings. Material questions (Buna-N vs EPDM vs silicone)? See the rubber material guide. Service shops and manufacturers: bulk pricing available.