Set contains 7 blades from 1/4″ to 5/8″ arbor, pilot and holder. Each blade will cut over 3,000 holes in sheet metal. New blades thread onto arbor easily and the adjusting screw makes minute depth control of cuts possible. Depth rod determines the distance the retracting pin can receded and thereby adjusts to the depth of cut. Fits any 1/4″ drill.