Dottie Spade drill bit has a decimal equivalent of 1.375-inches, fractional size of 1-3/8-Inch and a diameter of 1-3/8-inches. The 6-Inch drill bit has cold forged steel for durability. It is fully heat treated to extend bit life and individually stamped with size. It is suitable for boring hardwoods, softwood, plywood and drywall.