Design Professional It is very suitable to use mortise machine or mortise accessory to drill square holes in wood(br) Suitable for all mortiser and drill accessories(br) Square hole drill bits are principally used in woodworking(br) [Material and size] Made of high speed steel(br) Heat treatment, high hardness, long core, high concentricity; 4 different sizes include 1/4 " (6(br)35mm), 5/16 " (7(br)94mm), 3/8 " (9(br)5mm), 1/2 " (12(br)7mm) ))) [Why choose this project] Reduce the labor intensity of construction workers, speed up construction and reduce construction costs in construction, installation, decoration and decoration industries(br) / p> [Package contents] 1 pieces 1/4 " (6(br)35mm); 1 piece 5/16 " (7(br)94 mm); 1 piece of 3/8 " (9(br)5 mm); 1 piece of 1/2 " (12(br)7 mm) [Note] Drilling square holes requires tools such as power drills and hammers(br) (None of the above)