DESIGNED Professional Great for drilling square holes in wood with a mortising machine or a mortising attachment.Fits all mortising machines and drill press attachments. Square hole drill is mainly used for woodworking aspects. MATERIAL and SIZE Made of high-speed steel. Heat treatment, HRC48~50, high hardness, lengthened core, high concentricity; 4 Different size include 1/4" (6.35mm), 5/16" (7.94mm), 3/8" (9.5mm), 1/2" (12.7mm) WHY CHOOSE THIS ITEMReduce labor intensity of construction workers, speed up the construction speed, reduce construction costs for construction, installation, renovation, decoration industries. PACKAGE CONTENT 1Pcs 1/4" (6.35mm); 1Pcs 5/16" (7.94mm); 1Pcs 3/8" (9.5mm); 1Pcs 1/2" (12.7mm) NOTEThe square hole punching needs to use electric drill, hammer and other tools.(All of these are not include)