AS568-251 FKM Fluorocarbon O-Ring, 70A Durometer, 5 1/8" ID x 1/8" CS (5.109" x 0.139" Actual, 5.387" OD) - Precision-Molded Replacement Sealing Ring for Pumps, Valves, Filters, Gearboxes & Hydraulics

FINAL SALE - NO RETURNS. THIS IS A STANDARD CATALOGUE SIZE; CONFIRM YOUR INSIDE DIAMETER, CROSS-SECTION AND MATERIAL BEFORE ORDERING.

Every dimension, material and durometer for this o-ring is published above. Because these are standard catalogue sizes chosen by measurement rather than by pump model, they ship as final sale. If we send the wrong item, or it arrives damaged or defective, we replace it free of charge - that never changes.

Chasing a leak or a slow drip and need the exact o-ring size to seal it for good? A worn or wrong-size o-ring lets fluid weep past the joint, drops pressure, and can damage the equipment around it.

This Beaver Island Parts Company replacement o-ring is a single AS568-251 o-ring, a universal industry-standard size. Its nominal size is 5 1/8" inside diameter by 1/8" cross-section; the actual measured dimensions are 5.109" ID by 0.139" CS, held to a tolerance of ±0.035" on the ID and ±0.004" on the CS, for a 5.387" outer diameter. It is molded in 70A Fluorocarbon (FKM) rubber and is a drop-in replacement for any standard dash-251 o-ring.

Full Compatibility: AS568-251 is a standard o-ring dash size used across pumps, filters, valves, gearboxes, hydraulic fittings, plumbing and countless machines. If your application calls for a 5.109" ID x 0.139" CS o-ring, this is the size.
Installation Note: Clean the groove, inspect the sealing surface, seat the new o-ring without twisting it, and lubricate before assembly. No special tools are required for most o-ring changes.
Pro Tip: Apply Aqua Flex lubricant to the o-ring before installation to ease seating and extend seal life.

We are an American family-owned and operated small business committed to providing high-quality replacement parts and straightforward, honest fitment information so you can fix it once and get back to work.