1、4 PCS SET: This kit includes 4 pcs step drill bits, with the specifications of 4 to 20mm straight grooved type, 4 to 20mm and 4 to 22mm spiral grooved type. 2、HIGH EFFICIENCY: The step drill bit with straight grooved ensures large chip removal and quick drilling, and the drill bit with spiral grooved could reduce cutting resistance for faster and smoother cutting. 3、INDUSTRIAL STEEL: The step drill bit is made of industrial grade steel and can provide maximum strength when processing various plates or surfaces (such as metal, wood, plastic, aluminum, or copper). 4、WIDELY COMPATIBLE: These step bits are compatible with most impact power tools, electric drills, bench drills, and can be connected to extension rod. 5、MULTI PURPOSE: Whether for DIY projects or professional engineering purposes, this step drill bit kit can easily meet your punching and drilling needs.