This Threaded Prop Adapter is the same one that is included with 4020, and 4025 series Scorpion Brushless motors. Machined from High-Quality Aluminum bar stock, it is designed to fit on a 6mm motor shaft, and has an 8mm threaded prop shaft. The thread pitch on the shaft is a metric fine 8 x 1.0mm size. The prop shaft length is 33mm (1.30 inches) so there is plenty of room for a prop and spinner back-plate. The Scorpion 6mm Threaded Prop Adapter weighs 22 grams, and can be used on any brushless motor with a 6mm shaft.