Flanged seacock installation is improved with the use of a backing block between the valve flange and the hull. Size 4.29" Dia. Fits 3/4" & 1" Seacocks Bolt 5/16" - 18"

• Each size fits multiple seacock sizes.


• Press threaded inserts into the hull side of the backing block into the holes that match the seacock flange.


• 1/2" thickness is rigid enough for a secure installation but flexible enough to conform to minor hull curvature.


• Will not swell or absorb moisture.