Fluke tltp175 twistguard test probes and leads sets fluke fluke tp175 the fluke tp175 twistguard test probe set has important new features to conform to the latest test standards by twisting the probe the operator can adjust the length of the exposed metal tip which satisfies the requirement in en 61010 031 that there should be less than 4mm of conductive tip for cat iii and cat iv instruments a window near the probe tip shows the cat rating of the current tip exposure such as cat ii 1000