Finer Power NBR 70 O-Ring, inside diameter - id (inch) 21

NBR (nitrile rubber) 70 durometer O-rings in the BS series with a 1/4" nominal cross section (6.99mm).

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
• 51 BS part numbers, 4-1/2 to 26" inside diameter
• Nominal cross section 1/4" (6.99mm)
• Nominal and measured dimensions in inches and millimetres

Key specifications

Sizes available

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, 3/16" Cross Section, 7/16 to 4-5/8" 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.