Specifications:The whole drill is heat treated, offering higher hardness.This Mortising Chisel is great for drilling square holes in wood with a mortising machine or a mortising attachment.Mainly used in the square tenon machine, specially used for a drill square hole, and it also can be used on electric drill.Item Name: Square Hole Drill BitMaterial: High Speed SteelSquare Hole Drill Core: More than 210mmCylinder Diameter of the Fixed Part: 19mmProduct Attributes: 1/4", 5/16", 3/8", 1/2"Product Specifications: 1/4"(6.35mm), 5/16"(7.94mm), 3/8"(9.5mm), 1/2"(12.7mm)Features: Durable, Practical, Woodworking Tools, Square HoleProduct Size: Length: 21.5cm/8.46", 20.9cm/8.23" (Approx.)Notes:Due to the light and screen setting difference, the item's color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement.Package Includes:1 x Square Hole Drill Bit