describe Professionally designed and perfect for drilling square holes in wood with a mortiser. Suitable for all rigging and accessories. Square hole drill bits are mainly used in the woodworking field. Material and Dimensions: Made of high speed steel. Heat treatment, HRC48~50, high hardness, slender center, high concentricity; 4 sizes: 1/4" (6.35 mm), 5/16" (7.94 mm), 3/8" (9.5 mm), 1/2" (12.7 mm). Why choose this project: It reduces the labor intensity of construction personnel, and at the same time speeds up the work and reduces the cost. Ideal for the construction, renovation and decoration industries. Supplied with: 1 piece 1/4" (6.35 mm), 1 piece 5/16" (7.94 mm), 1 piece 3/8" (9.5 mm), 1 piece 1/2" (12.7 mm), Note: The attack angle needs to use a drill, hammer or other tools. (None of these are included). Note: 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. Sold by-YJL official store