Finer Power NBR 70 O-Ring, 3-7/8
Available
NBR (nitrile rubber) 70 durometer O-rings in the BS series with a 3/16" nominal cross section (5.33mm).
An O-ring seals a joint by sitting in a groove and being squeezed between two surfaces, and nitrile rubber is a common choice for oils, fuels and hydraulic fluids. Each part number below comes in its inside diameter, outside diameter and cross section in inches, the measured dimensions with tolerances, and the pack quantity where one applies.
Where this product is used
- Sealing flanges, covers and housings in machinery
- Sealing hydraulic and pneumatic fittings, cylinders and valves
- Sealing pump, gearbox and filter housings
- Replacing worn or damaged O-rings during maintenance
Features
- Nitrile rubber (NBR), 70 durometer
- 42 BS part numbers, 7/16 to 4-5/8" inside diameter
- Nominal cross section 3/16" (5.33mm)
- Nominal and measured dimensions in inches and millimetres
- Pack quantities of 5, 10 and 20, by size
Key specifications
| Specification | Detail |
|---|---|
| Material | Nitrile rubber (NBR) |
| Hardness | 70 durometer |
| Series | BS (imperial) |
| Cross section | 3/16" (5.33mm) |
| Inside diameter | 7/16 to 4-5/8" |
| Sizes | 42 part numbers |
Sizes available
| Part number | ID (in) | OD (in) | Cross section (in) | ID (mm) | Cross section (mm) | Pack |
|---|---|---|---|---|---|---|
| BS309 | 7/16 | 13/16 | 3/16 | 10.46 ± 0.13 | 5.33 ± 0.13 | 20 |
| BS310 | 1/2 | 7/8 | 3/16 | 12.07 ± 0.13 | 5.33 ± 0.13 | 20 |
| BS311 | 9/16 | 15/16 | 3/16 | 13.64 ± 0.18 | 5.33 ± 0.13 | 20 |
| BS312 | 5/8 | 1 | 3/16 | 15.24 ± 0.23 | 5.33 ± 0.13 | 20 |
| BS313 | 11/16 | 1-1/16 | 3/16 | 16.81 ± 0.23 | 5.33 ± 0.13 | 20 |
| BS314 | 3/4 | 1-1/8 | 3/16 | 18.42 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS315 | 13/16 | 1-3/16 | 3/16 | 19.99 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS316 | 7/8 | 1-1/4 | 3/16 | 21.59 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS317 | 15/16 | 1-5/16 | 3/16 | 23.16 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS318 | 1 | 1-3/8 | 3/16 | 24.77 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS319 | 1-1/16 | 1-7/16 | 3/16 | 26.34 ± 0.25 | 5.33 ± 0.13 | 20 |
| BS320 | 1-1/8 | 1-1/2 | 3/16 | 27.94 ± 0.3 | 5.33 ± 0.13 | 20 |
| BS321 | 1-3/16 | 1-9/16 | 3/16 | 29.51 ± 0.3 | 5.33 ± 0.13 | 10 |
| BS322 | 1-1/4 | 1-5/8 | 3/16 | 31.12 ± 0.3 | 5.33 ± 0.13 | 10 |
| BS323 | 1-5/16 | 1-11/16 | 3/16 | 32.69 ± 0.3 | 5.33 ± 0.13 | 10 |
| BS324 | 1-3/8 | 1-3/4 | 3/16 | 34.29 ± 0.3 | 5.33 ± 0.13 | 10 |
| BS325 | 1-1/2 | 1-7/8 | 3/16 | 37.47 ± 0.38 | 5.33 ± 0.13 | 10 |
| BS326 | 1-5/8 | 2 | 3/16 | 40.64 ± 0.38 | 5.33 ± 0.13 | 10 |
| BS327 | 1-3/4 | 2-1/8 | 3/16 | 43.82 ± 0.38 | 5.33 ± 0.13 | 10 |
| BS328 | 1-7/8 | 2-1/4 | 3/16 | 46.99 ± 0.38 | 5.33 ± 0.13 | 10 |
| BS329 | 2 | 2-3/8 | 3/16 | 50.17 ± 0.46 | 5.33 ± 0.13 | 10 |
| BS330 | 2-1/8 | 2-1/2 | 3/16 | 53.34 ± 0.46 | 5.33 ± 0.13 | 10 |
| BS331 | 2-1/4 | 2-5/8 | 3/16 | 56.52 ± 0.46 | 5.33 ± 0.13 | 5 |
| BS332 | 2-3/8 | 2-3/4 | 3/16 | 59.69 ± 0.46 | 5.33 ± 0.13 | 5 |
| BS333 | 2-1/2 | 2-7/8 | 3/16 | 62.87 ± 0.51 | 5.33 ± 0.13 | 5 |
| BS334 | 2-5/8 | 3 | 3/16 | 66.04 ± 0.51 | 5.33 ± 0.13 | 5 |
| BS335 | 2-3/4 | 3-1/8 | 3/16 | 69.22 ± 0.51 | 5.33 ± 0.13 | 5 |
| BS336 | 2-7/8 | 3-1/4 | 3/16 | 72.39 ± 0.51 | 5.33 ± 0.13 | 5 |
| BS337 | 3 | 3-3/8 | 3/16 | 75.57 ± 0.61 | 5.33 ± 0.13 | 5 |
| BS338 | 3-1/8 | 3-1/2 | 3/16 | 78.74 ± 0.61 | 5.33 ± 0.13 | 5 |
| BS339 | 3-1/4 | 3-5/8 | 3/16 | 81.92 ± 0.61 | 5.33 ± 0.13 | 5 |
| BS340 | 3-3/8 | 3-3/4 | 3/16 | 85.09 ± 0.61 | 5.33 ± 0.13 | 5 |
| BS341 | 3-1/2 | 3-7/8 | 3/16 | 88.27 ± 0.61 | 5.33 ± 0.13 | 5 |
| BS342 | 3-5/8 | 4 | 3/16 | 91.44 ± 0.71 | 5.33 ± 0.13 | 5 |
| BS343 | 3-3/4 | 4-1/8 | 3/16 | 94.62 ± 0.71 | 5.33 ± 0.13 | - |
| BS344 | 3-7/8 | 4-1/4 | 3/16 | 97.79 ± 0.71 | 5.33 ± 0.13 | - |
| BS345 | 4 | 4-3/8 | 3/16 | 100.97 ± 0.71 | 5.33 ± 0.13 | - |
| BS346 | 4-1/8 | 4-1/2 | 3/16 | 104.14 ± 0.71 | 5.33 ± 0.13 | - |
| BS347 | 4-1/4 | 4-5/8 | 3/16 | 107.32 ± 0.76 | 5.33 ± 0.13 | - |
| BS348 | 4-3/8 | 4-3/4 | 3/16 | 110.49 ± 0.76 | 5.33 ± 0.13 | - |
| BS349 | 4-1/2 | 4-7/8 | 3/16 | 113.67 ± 0.76 | 5.33 ± 0.13 | - |
| BS350 | 4-5/8 | 5 | 3/16 | 116.84 ± 0.76 | 5.33 ± 0.13 | - |
Choosing the right option
Choose the O-ring from the groove it fits: the inside diameter, the cross section and the part number. To match an existing O-ring, measure the cross section with calipers and the inside diameter with the O-ring relaxed, then pick the closest part number. The digit after BS in most part numbers gives the cross section series: BS0 is 1/16", BS1 is 3/32", BS2 is 1/8", BS3 is 3/16" and BS4 is 1/4".
Other BS series cross sections are under NBR 70 O-Ring, BS Series, 1/16" Cross Section, 1/16 to 5-1/4" ID; NBR 70 O-Ring, BS Series, 3/32" Cross Section, 1/16 to 9-3/4" ID; NBR 70 O-Ring, BS Series, 1/8" Cross Section, 3/16 to 18" ID; NBR 70 O-Ring, BS Series, 1/4" Cross Section, 4-1/2 to 26" ID. For a size that is not stocked, NBR 70 O-Ring Cord, Imperial, 1/16 to 1/2 in Diameter can be cut and joined to make a seal for a non-standard groove.
Nitrile rubber suits many oils, fuels and hydraulic fluids. Check that the fluid and the operating conditions suit nitrile before fitting.
| Option | Part number | SKU |
|---|---|---|
| 1/2 | BS310 | A0125816 |
| 1 | BS318 | A0125824 |
| 1-1/16 | BS319 | A0125825 |
| 1-1/8 | BS320 | A0125826 |
| 1-3/16 | BS321 | A0125827 |
| 1-1/4 | BS322 | A0125828 |
| 1-5/16 | BS323 | A0125829 |
| 1-3/8 | BS324 | A0125830 |
| 1-1/2 | BS325 | A0125831 |
| 1-5/8 | BS326 | A0125832 |
| 1-3/4 | BS327 | A0125833 |
| 1-7/8 | BS328 | A0125834 |
| 2 | BS329 | A0125835 |
| 2-1/8 | BS330 | A0125836 |
| 2-1/4 | BS331 | A0125837 |
| 2-3/8 | BS332 | A0125838 |
| 2-1/2 | BS333 | A0125839 |
| 2-5/8 | BS334 | A0125840 |
| 2-3/4 | BS335 | A0125841 |
| 2-7/8 | BS336 | A0125842 |
| 3/4 | BS314 | A0125820 |
| 3 | BS337 | A0125843 |
| 3-1/8 | BS338 | A0125844 |
| 3-1/4 | BS339 | A0125845 |
| 3-3/8 | BS340 | A0125846 |
| 3-1/2 | BS341 | A0125847 |
| 3-5/8 | BS342 | A0125848 |
| 3-3/4 | BS343 | A0125849 |
| 3-7/8 | BS344 | A0125850 |
| 4 | BS345 | A0125851 |
| 4-1/8 | BS346 | A0125852 |
| 4-1/4 | BS347 | A0125853 |
| 4-3/8 | BS348 | A0125854 |
| 4-1/2 | BS349 | A0125855 |
| 4-5/8 | BS350 | A0125856 |
| 5/8 | BS312 | A0125818 |
| 7/16 | BS309 | A0125815 |
| 7/8 | BS316 | A0125822 |
| 9/16 | BS311 | A0125817 |
| 11/16 | BS313 | A0125819 |
| 13/16 | BS315 | A0125821 |
| 15/16 | BS317 | A0125823 |
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NBR 70 O-Ring, BS Series, 3/16 in Cross Section, 7/16 to 4-5/8 in ID: 3-7/8
SKU: A0125850 | Model: BS344
NBR 70 O-ring BS344, 3-7/8" ID x 3/16" cross section (97.79 x 5.33mm). Nitrile rubber, 70 durometer.
