Description: --5PCS High speed steel HSS high hardness step drill bit metric cone drill bit set. --Titanium coated to reduce friction and heat. --No need to use center punch, not easy to break compared with ordinary twist drill. --Automatically deburrs, chamfer, open hole expansion, make a clean hole as you drill. --Use tools: drill, bench drill. --The recommended drilling speed is 250-400 rpm. --Suit for cutting holes in a variety of materials including thin metals, steel aluminium, copper, wood, plastic, fiberglass, brass and PVC etc.. Specification: Material: High-speed Steel Drill size: (3/16，1/4，5/16，3/8，7/16，1/2) (1/8,5/32.7/32.1/4,9/32,5/16,11/32,3/8,13/32,7/16,15/32,1/2mm) (1/4,5/16,3/8,7/16,1/2,9/16,5/8,11/16,3/4) (3/16，1/4，5/16，3/8，7/16，1/2，9/16，5/8，11/16，3/4，13/16，7/8) (1/4，3/8，1/2，5/8，3/4，7/8，1，1-1/8，1-1/4，1-3/8) Package Includes: 5 Pieces /Set Step Drill Bit