Bosch HDG138QA 3-Piece Diamond Hole Saw Set Vacuum-brazed diamond grit cuts faster and lasts longer Segmented teeth reduce debris and heat AutoStart pilot bit is spring-loaded, retractable shaft allows walk-free cutting without a pilot hole Pilot bit offers unique grind that starts holes accurately every time Plastic case Set includes: (1) mandrel, (1) AutoStart pilot bit, (1) 1-3/8 inch hole saw