The AndyMark 11 Tooth 0.6 Module 0.125in. Round Bore Steel Pinion Gear is designed to securely attach to the knurled shaft of a 9015 motor through a friction press fit, eliminating the need for additional securing components such as set screws or clamps. This gear is specifically compatible with the 9015 motor and is not suitable for smooth shafts like those on the Banebots 550 motor. It can be utilized as a pinion gear in PG27 gearboxes when the motor is switched to a 9015.