Wood flat bit is forged in one piece from high carbon steel. The hardness of the cutting point and the blade is 50 HRC. It is used to drill in all types of wood,Website:http://www.hzgshardwares.com,such as soft and close grained wood, chipboard and floor board. Part No Metric Imperial GS-B40006 6mm 1/4” GS-B40008 8mm 5/16” GS-B40010 10mm 3/8” GS-B40012 12mm 15/32” GS-B40014 14mm 9/16” GS-B40016 16mm 5/8” GS-B40018 18mm 11/16” GS-B40020 20mm 25/32”” GS-B40022 22mm 7/8” GS-B40024 24mm 15/16” GS-B40025 25mm 1” GS-B40028 28mm 1-1/8” GS-B40030 30mm 1-3/16” GS-B40035 35mm 1-3/8” GS-B40038 38mm 1-1/2” GS-B40040 40mm 1-9/16”