On one end is a metal plate which has a semicircular ring attached at a right angle. On the other end are a series of slots punched in the rubber. Put the cuff around a wrist, ankle, or upper arm, then insert the ring through whichever slot gives you the fit you need. Put a lock, hook, or rope through the ring, and the cuff is secure. For a general-purpose set, we usually recommend the medium sizes.
Prices are per pair.
Locks not included.