Four pole 1.65" (42mm) slotless brushless motors (from Koford Engineering) offer stall torque up to 225 oz-in and a peak power of 74 watts at 1585 rpm. Continuous power is 63 W. Oversize bearings and 1/4" shaft purportedly make this motor well suited for medical or military pumps as well as servo applications. The motors feature a diameter of 1.65", a length of 2.569", a weight of 15 oz., and peak efficiency of 84%. The 4 pole design provides double the speed resolution compared to two-pole motors. 120° hall sensors or sensorless versions are available.