The Perko Bronze Thru-Hull Fittings are threaded with NPS (straight) male pipe thread, and are for use with compatible seacocks or with any product with straight female pipe thread. The machined flange is grooved on the underside to retain bedding compound.
The use of these fittings on products with NPT (tapered) pipe thread is recommended only for low pressure applications, and then only with a generous application of pipe sealant or PTFE thread tape.
Perko Bronze Thru-Hull Fittings are the perferred choice for below-the-waterline use. They are supplied complete with a bronze locknut.