Adapter eliminates dangerous thread mis-matches between thru-hulls and in-line valves and valve damage in OEM installations. Accepts a standard thru-hull fitting into the base and a standard in-line valve (or other tapered thread component) on top. Also provides a safe, sturdy assembly when in-line valves are used as seacocks. Pipe 1-1/2" NPS to 1-1/2" NPT