HRC 48-50 STEEL: Made of special steel with heat treatment, these drills have a high hardness reaching HRC 48-50, an elongated core and high concentricity for long-lasting use. 6 SLOT DIAMETER: With 6 pieces per pack, these saw bits have different diameters of 1/4 inch (6.4 mm), 5/16 inch (8 mm), 3/8 inch (9.5 mm), 1/2 inch (12.7 mm), 9/16 inch (14 mm), and 5/8 inch (16 mm). MATCH FOR DOUBLE EFFECT: Achieve enhanced performance when used with mortising machines; square hole cutting requires electric drill, hammer, and other compatible tools. WIDELY APPLICABLE: Ideal accessory for mortising, chiseling, and woodworking applications; suitable for construction, installation, renovation, and decoration industries.