Libra 2 Hydraulic Uni-servo Cylinders for 10"/12" Hydrualic Marine Trailer Brake - 21044 2 new hydraulic brake uni-servo cylinders for 10"x2-1/4" and 12"x2" hydraulic trailer brakes Aluminum for marine application The listing has 2 cylinder kits, replacement for 2 brakes Kits include: 1 left and 1 right cylinders with link arms