A new micro metal gear motor with a difference! This motor comes with a built-in encoder which measures the motor's speed in real time. The average output number of pulses can reach up to 300 pulses per revolution. The motor has a long (0.354"/9.0 mm) D profile metal output shaft that is compatible with the 42x19mm and 32x7mm dimensions of the Pololu wheel. The brass faceplate has two mounting holes threaded for M1.6 screws (1.6mm diameter, 0.35mm thread pitch), or you can use the mounting bracket or extended mounting bracket which are specifically designed to securely mount the gear motor while enclosing the exposed gears. We recommend the extended mounting bracket for wheels with recessed hubs, such as the 42×19mm wheel.