This prop adapter was designed to be used on the Scorpion 30mm series motors, or any other motor with a 5mm shaft diameter. These prop adapters have an extra long shaft that measures 48mm total length, with 37mm of shaft forward from the prop back plate. THis prop adapter is long enough to work with the thickest hubs on high pitched propr, and still have enough thread to allow for a plastic spinner with a thick backplate.