Aeromarine .250" (6.375mm) replacement brass collet insert. This is for the larger collet that uses a 5/8" wrench. This item DOES NOT come with the coupler body itself. THIS is ONLY the Replacement brass insert/collet. NOTE: AeroMarine sells two different style coupler bodies.The smaller one uses a 9/16" wrench. The larger one uses a 5/8" wrench.