Delta Power Equipment Corporation 17-001 1/4-Inch Professional Mortising Chisel and Bit Set Contains 1 Chisel and Bit Set Size: 1/4 in. square Bits made of high-quality steel andresist overheating in heavy use Designed with a 5/8 in. shank to fit DELTA products; also fits most brands of Mortisers and Drill Press Attachments