Rubber O-rings and O-ring seals in nitrile (Buna-N NBR 70A): 7 stocked items from $2.07, from a 1/4" ID #010 to a large-diameter 5-1/2" ID #357, plus the OR-100 replacement O-ring for Big Blue and Pentek filter housings. The small sizes come in 100-packs. Orders ship from Elgin, SC, usually within 24 hours.
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.
Rubber O-ring size chart (nitrile Buna-N, 70A)
| Dash size |
ID |
OD |
Cross-section |
Pack |
| #010 |
1/4" |
3/8" |
1/16" |
100 |
| #011 |
5/16" |
7/16" |
1/16" |
100 |
| #017 |
11/16" |
13/16" |
1/16" |
100 |
| #121 |
1-1/16" |
1-1/4" |
3/32" |
100 |
| #230 |
2-1/2" |
2-3/4" |
1/8" |
10 |
| #357 |
5-1/2" |
5-7/8" |
3/16" |
1 |
| OR-100 (151122) |
— |
— |
— |
1 |
Rubber O-ring FAQ
Do you have large diameter rubber O-rings?
Yes. The #357 is 5-1/2" ID x 5-7/8" OD x 3/16" cross-section and is sold singly; the #230 is 2-1/2" ID x 2-3/4" OD x 1/8" cross-section in a 10-pack.
What do the O-ring numbers (#010, #230, #357) mean?
They are the standard AS568 dash sizes. Every listing also gives the inside diameter, outside diameter and cross-section in inches, so you can match an O-ring by measurement.
What are these rubber O-rings made of?
The dash-size O-rings are nitrile rubber (Buna-N / NBR) at 70A durometer, as listed on each product. The OR-100 (151122) replacement for Big Blue / Pentek filter housings is also Buna-N.
How do I find the right O-ring size?
Measure the inside diameter (ID) and the cross-section (CS, the thickness of the ring). The outside diameter is ID plus two cross-sections: for example #010 is 1/4" ID + 2 × 1/16" CS = 3/8" OD. Match ID and CS to the table above.
Do you sell rubber O-rings in packs?
Yes. #010, #011, #017 and #121 come in 100-packs, #230 in a 10-pack, and the large #357 (5-1/2" ID) singly. Bulk discounts show in the price breakdown on each product page.
O-ring or rubber washer: which one do I need?
An O-ring seals in a groove or around a shaft; a flat rubber washer seals under a bolt head or between two flat faces.
How fast do O-rings ship?
Orders usually ship within 24 hours by UPS or FedEx with tracking from our warehouse in Elgin, South Carolina; orders over $199 ship free to the East & Central US (West Coast, Alaska & Hawaii: free over $399).
Related: Rubber washers · Rubber plugs for holes · Rubber grommets
Sealing a flat face, such as a faucet seat, hose fitting or bolt head, rather than a groove? A flat washer is usually the better part. See rubber washer vs. O-ring at our sister store Rubber Washer Warehouse.
Find your O-ring size: look up a dash number in the AS568 O-ring size chart, or enter what you measured in the O-ring size calculator to get the ID, OD, cross-section and groove dimensions. Fixing a leaking filter housing? Start with the water filter housing O-ring guide.
More O-ring questions
Are these industrial O-rings?
Yes. They are standard AS568 dash sizes in nitrile (Buna-N / NBR) at 70A durometer, the general-purpose industrial compound for water, air, petroleum oils, fuels and hydraulic fluids, rated -40°F to 250°F.
When should I not use a nitrile O-ring?
Nitrile is not recommended for ozone or direct sunlight, brake fluid, ketones or strong acids. Check the rubber compatibility chart before using these O-rings with chemicals.
Can an O-ring be used as a gasket?
An O-ring is a gasket for grooves and round joints: it seals when it is squeezed in a groove or against a fitting face. For a flat joint, such as under a bolt head or between two flat flanges, a flat rubber washer is the better part. See gasket vs washer vs O-ring.
Which O-ring fits a Big Blue water filter housing?
The 10" and 20" Big Blue housings use the Pentek 151122 / OR-100 ring, an AS568 #357 (5-1/2" ID x 3/16" cross-section). See the water filter housing O-ring guide and the 15-minute Big Blue leak fix.
My size is not listed. What should I do?
We stock the sizes in the table above. To identify your ring, use the AS568 O-ring size chart or the O-ring size calculator (ID, cross-section, OD and groove), then match the dash number. For larger quantities of a stocked size, see bulk orders.
Also searched as: o ring, oring, round seals.
Sizing help: How to measure an O-ring · All guides & size charts
O-rings in stock now: size and price chart
Every O-ring below is in stock today and ships from Elgin, SC. All dash sizes are nitrile (Buna-N / NBR) 70A, AS568 standard. Click a size to order.
| Size |
ID |
OD |
Cross-section |
Pack |
Price |
| #008 |
3/16" |
5/16" |
1/16" |
100 |
$6.44 |
| #010 |
1/4" |
3/8" |
1/16" |
100 |
$6.44 |
| #011 |
5/16" |
7/16" |
1/16" |
100 |
$6.90 |
| #014 |
1/2" |
5/8" |
1/16" |
100 |
$4.57 |
| #017 |
11/16" |
13/16" |
1/16" |
100 |
$4.10 |
| #121 |
1-1/16" |
1-1/4" |
3/32" |
100 |
$17.48 |
| #230 |
2-1/2" |
2-3/4" |
1/8" |
10 |
$4.60 |
| #357 |
5-1/2" |
5-7/8" |
3/16" |
1 |
$2.07 |
| OR-100 (151122) |
Big Blue / Pentek housing |
— |
— |
1 |
$2.07 |
Where these O-ring sizes are used
-
1/16" cross-section (#008–#017): small fittings, faucet cartridges, spray nozzles, pneumatic push-fittings and small pump shafts.
-
3/32" cross-section (#121): 1" class pipe and hose fittings, filter caps and sight glasses.
-
1/8" cross-section (#230): housings, end caps and covers around 2-1/2".
-
3/16" cross-section (#357) and OR-100: large filter housings (Big Blue, Pentek), tank lids and pump volutes.
Buna-N is right for water, air, petroleum oils, greases and hydraulic fluid. For steam, outdoor ozone or drinking-water seals that need EPDM, or food and high-heat seals that need silicone, use a flat washer in that compound from our sister store's EPDM washers or silicone washers.
More O-ring answers
How much should an O-ring stretch? About 1–5% over the shaft or groove diameter; more than that thins the cross-section and it can leak.
Should I lubricate an O-ring? Yes, a thin film of silicone grease (or a lubricant compatible with the fluid) stops it twisting or nicking as it seats. Never use petroleum grease on EPDM.
Can I reuse an O-ring? Replace it if it is flattened, cracked, hard or nicked; a flattened ring no longer has the 20–30% squeeze it needs to seal.
Related: rubber washers · rubber hole plugs · rubber grommets
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