The hard plastic slip x slip bulkheads with rubber gasket is great for use with wet/dry filters and sump systems in freshwater or marine setups. The Hard plastic bulkheads with rubber gasket are threaded on outside; smooth on inside for slip fitting on both ends.

1/2 inch Bulkhead requires 1.25 inch hole

3/4 inch Bulkhead requires 1.50 inch hole

1 inch Bulkhead requires 1.75 inch hole

1.5 inch Bulkhead requires 2.5 inch hole