Double ended drill bits are derivative of HSS-G and both ends are drills like double headed bits. Materials / Same material as HSS-G and fully ground. Cutting edge / 135° split point geometry which ensures no walking and slipping. The total and working lengths are shorter than other HSS drill bits. Size / Total 21sizes from 2.0mm to 10.0mm including 3.1mm, 3.2mm, 3.3mm which are suitable sizes for drilling holes for rivets. Depth of hole / 30% shorter than HSS-G. Suitable for thin metal sheets because of the length. Package / Each size 10 pieces a pack. Application / While drilling many holes on thin metal sheets, double ended drill bits are preferred because of their short length and long life. Bit Dia x Length (mm) / 4.0 x 55 Working Length (mm) / 14.0 x 2 Pcs/Pkg. / 10