Groco BB Backing Block For Flanged Seacock 

Flanged seacock installation is improved with the use of a backing block between the valve flange and the hull.

• 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

Size: 4.29" Dia., Fits: 3/4" & 1" Seacocks, Bolt: 5/16" - 18"