These well proven adjustable countersinks are all supplied complete with an HSS twist drill & an allen key. They are designed to drill & countersink simultaneously a wide variety of materials. Choose TCT for abrasive materials. NOT SUITABLE FOR FERROUS & NON FERROUS METALS. T.C.T. No. 8 Wooscrew. Diameter: 5/8 in. Drill Diameter: 3/16 in. Overall Length: 1.1/4 in.