IVY Classic 10722 1-3/8 x 6-Inch Swift Bore Wood Spade Bit, High-Carbon Steel, 1/Card Drop-forged high-carbon steel for fast, smooth cutting of plywood, hard wood and soft wood, Swift Bore (Registered Trademark) Double-fluted chip removers with sharp spurs ensure faster cutting with a smooth finish Electronically heat treated and tempered to Rockwell Hardness 47-52 Precision ground and polished Diameter: 1-3/8-inch, Length: 6-inch, Shank: 1/4-inch quick-change power end hex