602-JJ-04 is a Marathon universal joint (UJ) shaft coupling assembly. It is used to connect two shafts that are not in alignment and to cushion the shock of sudden starting, stopping, and reversing of machinery. This coupling consists of two hubs, a spider assembly, and a mounting system. The hubs are manufactured from heat-treated steel and have a black oxide finish. The spider assembly is also made from steel and is designed with precision machine-ground ball bearings to facilitate smooth torque transmission. The mounting system, complete with screws and a mounting block, allows for installation in a variety of standard setups.