Material: Made of carbon steel, durable and practical, heat treated, long service life. 4 different sizes: 1/4" (6.35mm), 5/16" (7.94mm), 3/8" (9.5mm), 1/2" (12.7mm). This mortise and tenon chisel set is a must-have for home DIY enthusiasts. Ideal for drilling square holes in wood using a mortise machine or attachment mortise. Square hole drill bits are mainly used in woodworking. Reduce the labor intensity of construction personnel, speed up construction, and reduce construction, installation, renovation and maintenance costs. decoration. Note: It can achieve double effect when used in conjunction with a mortise and tenon machine. To drill square holes, you need to use tools such as electric drills and hammers. (These are not included). Note: The data is all measured manually, please allow 1-3cm error due to differences in light and display, there may be color differences, please refer to the actual item received.