The Scorpion HK-4525 motors are built with 10mm hardened steel shafts that will last through countless hours of flying fun, but occasionally, on a "Less than Perfect" landing, you may bend or break one. For these occasions, we offer factory replacement shafts for all the HK-4525 series Scorpion Helicopter Motors. The shaft for the HK-4525 series motors measures 10mm in diameter, and is 91.5mm in long. The pinion end of this shaft is ground down to 6mm to allow the user to install 6mm pinion gears. The shaft kit will also fit other brushless motors that require a 10mm shaft of this length. The shafts can be cut shorter with a Dremel tool and a cut-off wheel if necessary to fit other motors. Note: The shafts in the Scorpion motors are a slight press fit into the aluminum front housing. The shafts will not just slide out when the setscrews are removed. They need to be pressed out in a bearing press, or in a drill press, with the front housing of the motor supported in a block of wood to prevent warping the front housing. Weight including packaging 52.8g