The 12mm (507) Proton series motors are the new small motors for small planes and helicopters. These feature cooling holes in both the front and back cases for more cooling to allow harder running. The motors can be ordered with 1.5 or 2mm shafts. The front has 0-80 threaded mounting holes on a 8.5mm circle.Max RPM: 80,000Case Diameter: 12mmShaft: 1.5 or 2mm Shaft length: 7mmMounting screws are 0-80 threadAll Proton series motors have 6 slot stators and 4 pole rotors.