TL175 TwistGuard test leads have a manually adjustable test tip guard for different measurement environments. By twisting the lead, the user changes the exposed probe tip length from 4/25 in. (4 mm) to ¾ in. (19 mm). When the tip guard is fully extended, the leads are safety rated for Cat. 3 1,000 V and Cat. 4 600 V use. When the guard is retracted, the leads are safety rated for Cat. 2 1,000 V use.