This listing is for one replacement John Deere ball bearing, replaces codes GX21510. Measures 17mm X 40mm X 12mm and fits several mower spindles. Bearing specifications as follows: Outside dia.: 40mm Inside Dia.: 17mm Thickness: 12mm Sealed on both sides If you are not sure if these will fit your mower just send me an email with your model number and I will be happy to confirm them for you! One day handling!