Beckson screw-out plates provide access without the use of tools, with a single start, non-jamming (no cross-thread), extra strong, self-cleaning buttress thread. They incorporate a self-aligning center and an innovative gasket to assure a watertight seal. A unique back-up sealing wall leaves the plate water resistant, even if the gasket is removed. ID 4″ OD 6-1/8″ Hole 4-1/2″ Color White Center Smooth