#228 Nitrile O-Rings (10 Pack) - Buna-N NBR 70A - 2-1/4" ID x 2-1/2" OD x 1/8" CS
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Price per piece by quantity
- 1–49 pcs$4.95
- 50+ pcs$4.46
- 500+ pcs$3.96
- 1,000+ pcs$3.47
- 2,500+ pcs$2.97
- 5,000+ pcs$2.48
Bulk Discounts
| Quantity | Discounted price |
|---|---|
| Buy 1 – 49 pcs | $4.95 /each |
| Buy 50 – 499 pcs | $4.46 /each |
| Buy 500 – 999 pcs | $3.96 /each |
| Buy 1000 – 2499 pcs | $3.47 /each |
| Buy 2500 – 4999 pcs | $2.97 /each |
| Buy 5000 + pcs | $2.48 /each |
Need 5,000+ pieces or a recurring order? Request a bulk quote
#228 Nitrile O-Rings (10 Pack) - Buna-N NBR 70A - 2-1/4" ID x 2-1/2" OD x 1/8" CS is backordered and will ship as soon as it is back in stock.
Sizing help: O-ring size chart Inch ↔ mm converter
Couldn't load pickup availability
- Usually ships within 24 hours from Elgin, SC (shipping policy)
- UPS or FedEx with a tracking number on every order
- Returns accepted up to 30 days after delivery (return policy)
- Bulk discounts by quantity, quotes for large orders (request a quote)
- ID
- 2-1/4"
- OD
- 2-1/2"
- Material
- Nitrile (Buna-N / NBR)
Need more than one size?
Most of our multi-item orders mix sizes of the same part. Nearby sizes:
Quantities start at the $20.00-per-item minimum.
Description
Description
#228 Nitrile O-Ring (Buna-N NBR, 70A) - 2-1/4" ID x 2-1/2" OD x 1/8" CS
Standard AS568 dash size #228 nitrile O-ring - the exact size used across faucets, pumps, filters, and fittings worldwide. Sold as a pack of 10 so you have spares on hand for every rebuild.
Specifications
- AS568 Dash Number: -228
- Inside Diameter: 2-1/4" nominal (2.234" / 56.74 mm actual)
- Outside Diameter: 2-1/2"
- Cross Section (Width): 1/8" (0.139" / 3.53 mm)
- Material: Nitrile rubber (Buna-N / NBR)
- Hardness: 70A durometer
- Temperature Range: -40°F to 250°F
- Color: Black | Pack of 10
Material - Why Buna-N Nitrile
Buna-N is the workhorse O-ring compound: excellent resistance to petroleum oils, fuels, hydraulic fluids, water, and silicone greases, with good abrasion and tear resistance. Not recommended for ozone/direct sunlight exposure, brake fluid, ketones, or strong acids - for those, use EPDM or Viton.
Common Applications
Pool and spa pump unions, chlorinator lids, filter housings, large plumbing unions.
How to Measure an O-Ring
Measure the inside diameter (hole to hole) and the cross-section thickness of your old ring, or measure the groove: groove inner diameter = O-ring ID, groove width slightly wider than the cross section. Match both numbers to the chart below - the dash number takes care of the rest.
AS568 O-Ring Size Chart - Sizes We Stock
| Dash # | Inside Dia. | Outside Dia. | Cross Section | Metric ID |
|---|---|---|---|---|
| #010 | 1/4" (0.239") | 3/8" | 1/16" (0.070") | 6.07 mm ID |
| #011 | 5/16" (0.301") | 7/16" | 1/16" (0.070") | 7.65 mm ID |
| #017 | 11/16" (0.676") | 13/16" | 1/16" (0.070") | 17.17 mm ID |
| #121 | 1-1/16" (1.046") | 1-1/4" | 3/32" (0.103") | 26.57 mm ID |
| #228 (this size) | 2-1/4" (2.234") | 2-1/2" | 1/8" (0.139") | 56.74 mm ID |
| #230 | 2-1/2" (2.484") | 2-3/4" | 1/8" (0.139") | 63.09 mm ID |
| #238 | 3-1/2" (3.484") | 3-3/4" | 1/8" (0.139") | 88.49 mm ID |
| #357 | 5-1/2" (5.475") | 5-7/8" | 3/16" (0.210") | 139.07 mm ID |
Why Buy From Rubberfeetwarehouse
Genuine 70A Buna-N, ships fast from our South Carolina warehouse. Need a different size or larger quantity? Contact us.
Buna-N Material Guide
Buna-N Material Guide
Buna-N (Nitrile/NBR) 70A: excellent with petroleum oils, fuels, water, and hydraulic fluids. -40F to 250F. Not for ozone, brake fluid, or ketones - ask us about EPDM or Viton for those.
Delivery and Shipping
Delivery and Shipping
Usually ships within 24 hours from our South Carolina warehouse. All orders include tracking.
O-Ring Specifications
| AS568 Dash Number | -228 |
|---|---|
| Inside Diameter | 2-1/4" (57.15 mm) |
| Outside Diameter | 2-1/2" (63.5 mm) |
| Cross Section / Width | 1/8" (3.18 mm) |
| Shape | Round (torus) |
| Material | Nitrile (Buna-N / NBR) |
| Hardness | 70 Shore A |
| Finish / Color | Black |
| Temperature Range | -40°F to 250°F |
| Pack Quantity | 10 |
| Fits | AS568 -228 glands: 2-1/4" ID grooves, 1/8" cross section |
| Applications | Pool and spa pump unions, chlorinator lids, filter housings, large plumbing unions |
| SKU | ORING22810PCS |
AS568 nominal dimensions. Measure your groove ID and cross section to confirm fit.
Size & fit guide
| Label | Dimension | Size |
|---|---|---|
| A | Inside diameter | 2-1/4" 57.2 mm |
| B | Outside diameter | 2-1/2" 63.5 mm |
| C | Cross section | 1/8" 3.2 mm |
Schematic, not to scale. Sizes are nominal.
Fits
- AS568 -228 glands: 2-1/4" ID grooves, 1/8" cross section
Used for
- Pool
- spa pump unions
- chlorinator lids
- filter housings
- large plumbing unions
How to install
Wipe the groove clean and apply a thin film of silicone grease before seating the ring - it prevents pinching and doubles seal life on anything that gets opened regularly, like filter housings.
O-Ring Size Calculator
Enter your O-ring's inside diameter and cross-section — get the outside diameter and recommended static groove dimensions (25% squeeze).
Measuring a worn ring? Use calipers on ID and thickness — not the stretched old ring. Compound questions: rubber compatibility chart.
Frequently Asked Questions
What size is this O-ring?
AS568 dash number -228: 2-1/4" inside diameter, 2-1/2" outside diameter, 1/8" cross section.
How do I measure an O-ring?
Measure the inside diameter and the cross-section thickness of your old ring, or measure the groove: groove ID equals O-ring ID. Match both to the AS568 chart on this page.
Is Buna-N right for my application?
Buna-N (nitrile) handles petroleum oils, fuels, water, and hydraulic fluid from -40F to 250F. It is not for ozone/direct sun, brake fluid, or ketones - ask us about EPDM or Viton for those.
Should I lubricate O-rings at install?
Yes - a thin film of silicone grease prevents pinching and roughly doubles seal life on housings that get opened regularly, like water filter sumps.
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