Use this 1-3/8" retaining ring to secure your PTO shaft to the 1-3/8" input shaft of your shear bolt protected gearbox. This pins keeps the PTO shaft from coming off the gearbox and causing damage or bodily harm if the shear bolt shears. Don't risk your health operation a shear bolt protected implement without some for of PTO locking devise to keep it mounted to the shaft when the shear bolt shears. We sell many replacement parts for the most manufacturers rotary cutters. If you don't see the parts you need listed please contact us we would love to earn your business. We are listing new items frequently so please check our store often. We stock a wide variety of replacement parts for Agricultural Equipment please contact us if you have any questions or if you would like more information.