Brass air injector with spring check valve - tee fitting - 1/2" / 13mm barb Designed to allow multiple injector hook up off the one hose - up to 4 injectors per hose (3 tee, 1 elbow). Special 4 port manifold with 1/2" barbs, and 1/2" / 13mm hose available for these jets Hole size required - 14mm