This generic Flange Gasket is a Female (outside/thicker/smaller) fitting that is positioned between the elbow and the flange. This is the gasket that creates the watertight seal between the corrugated hose assembly and the bladder for the aircell (wing). Outer diameter is {1.56 in | 3.96 cm}. This is compatible with Dive Rite, DGX, Oxycheq and a wide variety of technical diving aircell brands on the market today.