This Is A Clear White Round Gasket Used On The Older Waterway Clearwater Sand Filter. This Is Used On Filters With The Clamp Style Valve. The New Split Nut Style Valve Uses an O-Ring.

This gasket is round with ridges and a slight lip at the inside edge

Dimensions:

Outside Diameter : 7-1/8"
Inside Diameter : 5-5/8"
Thickness : About 1/8" at the outside 1/4" at inside lip