Our urethane shackle bushings feature fluted grooves inside their inner bore so that, when used in conjunction with our greasable bolts, they can be kept greased for years of trouble-free, quiet operation! This bushing is a 1 in. OD (where it fits into the spring eye) and is designed to be used in a 2 1/2 in. wide spring. We use these bushings in our Jeep CJ rear shackle kits.