At Boston Gear, we manufacture our FC couplings from the highest quality alloy steel - not from powdered metal as many other industrial manufacturers do. Consisting of two metal jaws - or hubs - and an insert, this style of coupling is suited for high-torque and shock loads, does not require lubrication, and is not affected by oil, grease, dirt, or moisture. The allowable torque for the FC series of couplings is determined by the insert material. These inserts are the wearing member of the coupling and can be easily replaced with minimal effort.