5in Full Face Flange Gasket — Red Rubber 150#/125#, 1/8in Thick, 10in OD

A 5 inch full face gasket in 1/8 in. red rubber, cut to ASME B16.21 for 150 lb flanges. The bolt holes are cut through, so it drops over the bolts and locates itself. Pipe size is a name, not a measurement — 5 in. pipe is 5-9/16 in. across the outside, which is why the bore reads 5-9/16 in. and the outer edge 10 in.

Fits 150 lb and 125 lb flanges. 150 lb is the flange class, not a weight — it fixes the bolt pattern. Class 125 cast iron, the kind on Goulds, Berkeley, Cornell and Gorman-Rupp pump casings, uses the identical pattern, so one gasket covers both. A Class 300 flange is wider on a different bolt circle and takes a different gasket.

Where a 5 in. goes. Five inch is the odd size out — most pipe runs jump straight from 4 in. to 6 in., so plenty of suppliers skip it and the gaskets are awkward to track down. It turns up on older cast iron pump casings, fire and irrigation mains, and process lines laid before 6 in. became the default. It is also where the bolt holes step up from 3/4 in. to 7/8 in.

Red rubber (SBR) suits water, brine, air and low-pressure service. It is not a chemical gasket — for oil, fuel, solvents or acids you want Buna, Viton, EPDM or non-asbestos, and we cut all four.