Material: Made of high speed steel, high hardness up to HRC4850, durable and practical, heat treatment, long service life. 4 Different sizes: 1/4" (6.35 mm), 5/16" (7.94mm), 3/8" (9.5mm), 1/2" (12.7mm). This mortising chisel set is a must have for the home DIYer. Excellent for drilling square holes in wood with a mortising machine or mortising attachment. Square hole drill bit is mainly used for woodworking. Reduce labor intensity of construction workers, speed up construction speed, reduce cost in construction industries, of installation, renovation and decoration. Note:: They will achieve double effect by matched use with mortise and tenon machine, punching square holes need to use drill kettle, hammer and other tools. (None of these items are included). Package Dimensions: 23 x 13.6 x 3.1 cm; 600 grams Material