1-1/2in Full Face Flange Gasket — Red Rubber 150#/125#, 1/8in Thick, 5in OD

A 1-1/2 inch full face gasket in 1/8 in. red rubber, cut to ASME B16.21 for 150 lb flanges. Pipe size is a name, not a measurement — 1-1/2 in. pipe is 1.900 in. across the outside, and the gasket bore is cut at 1-7/8 in., rounded to the nearest eighth as it is on all the small sizes.

Fits 150 lb steel and 125 lb cast iron flanges — Class 125 and Class 150 share the same bolt pattern, so one gasket covers both. A Class 300 flange is wider on a different bolt circle and takes a different gasket. Red rubber (SBR) suits water, brine, air and low-pressure service; for oil, fuel, solvents or acids ask for Buna, Viton, EPDM or non-asbestos.

Where a 1-1/2 in. goes. Small circulators and booster pumps, pool and spa equipment, HVAC coil and branch connections, filter and valve manifolds. Below 2 in. most pipe runs are threaded or unioned rather than flanged, so a 1-1/2 in. flange is usually an equipment connection — a pump casing, strainer or valve body — rather than a length of pipe. It is also the first size down to 5/8 in. bolts instead of 3/4 in.