Torque wrench drives connect to a hydraulic pump and convert fluid pressure into force for turning fasteners. The pump allows setting the pressure to deliver the required torque to the drive. These drives accept interchangeable cassettes to match different-sized nuts and bolts. They turn the fastener from one end while a backup spanner locks down the other end, so the wrench can tighten or loosen the fastener and not just spin it.

Torque wrench cassettes have a slot to seat a torque wrench drive and a head that fits onto a nut or bolt. Their head sits at a right angle to the drive to maintain a low profile for working in spaces that would be too tight for a socket-style torque wrench.

Torque wrench reducers insert into the head of a compatible cassette and allow it to accept fasteners that are smaller than the stated cassette size. They extend the range of the cassette to minimize the need for cassette changes.