2, clear scale: easy to measure the distance from the edge of the door to the center of the required opening, 30-100MM measurable range, so that the opening is more accurate. 3, the hole cutter is not limited by the fixed: more convenient operation, can be moved with the electric drill, the hole cutter and the hole opener separate design. 1,Accurate positioning: easy to measure, matching opening position locator ruler, removable to make the opening more accurate. 4,Accurate limit, a key to open the hole: designed for 12MM depth and 35MM diameter holes, hexagonal shank easily without slipping., Manufacturer: Ounfhtrttk