High Quality Bulkhead fittings are the answer to pass a connection through a sealed wall. Creates a watertight seal with no gluing or screws and allows water to freely flow through of liquids. These are also called tank fittings and through hull fittings. Great for filters, skimmers, spillways, passing pipe through a pond wall, etc. The external Thread and nut are left hand threads. Internal thread on both ends is FPT. For use with tanks and liners having a wall thickness of 1/16" to 1/2". Easy through wall connection.