Precision engineered with stainless steel wire plugs. Features a specially designed file to cut and open tubes. The numbers are etched in black for better legibility. 14 ID sizes from 0.026 to 0.09 in and 22 OD sizes from 0.072 to 7/16 in (5 to 12 mm). Use both ID and OD calibrations to correctly determine tube size. Place tube in V-slot to measure OD. Pin gauge measures ID. The cap tube file is designed to cut and open the tube by filling a notch around the tubing at desired cutting point. Snap tube by bending at the notch and clean burrs by reaming out with the special file tip.