Buyouts 568-251 Standard O-Ring AS568 70 Durometer Buna-N NBR 5.109" ID x 0.139" CS

The Buyouts 568-251 is a standard AS568-251 O-ring manufactured from 70 Durometer Buna-N (NBR/Nitrile) rubber. This general-purpose sealing ring is widely used across industrial, hydraulic, pneumatic, and automotive applications wherever a reliable, oil-resistant seal is required.

Key Specifications:

• AS568 Size: 568-251
• Inner Diameter (ID): 5.109 in (129.77 mm)
• Cross-Section (CS): 0.139 in (3.53 mm)
• Outer Diameter (OD): Approximately 5.375 in (136.5 mm)
• Material: Buna-N (NBR) Nitrile Rubber
• Durometer Hardness: 70 Shore A
• Standard: AS568B / 568 Series

Material Properties:

• Excellent resistance to petroleum-based oils, fuels, and hydraulic fluids
• Good temperature range: approximately -40°F to +275°F (-40°C to +135°C)
• Resistant to water, mineral oils, and many solvents
• Not recommended for use with ketones, esters, or highly aromatic fuels

Buna-N O-rings conforming to AS568 standards are among the most commonly used seals in fluid power, plumbing, and mechanical systems. The 568-251 size is suitable for larger-bore applications such as pump housings, cylinder end caps, valve bodies, and industrial fittings. Sold in packs of 10.