Groco Backing Block for Seacocks, 1.25" TO 1.50". Flanged seacock installation is improved with the use of a backing block between the valve flange and the hull.

Features:

*Each size fits multiple seacock sizes.
*Press threaded brass inserts into the hull side of the backing block into the holes that match the seacock flange.
*Rigid 1/2" thickness provides secure installation but is flexible enough to conform to minor hull curvature.
*Will not swell or absorb moisture.
*Made from an environmentally friendly PVC foam specially formulated for marine applications.
* Measurements: 5.38" diameter with three 5/16"-18 threaded inserts.