These Faithfull Screwsinks can be used for drilling, countersinking and counter-boring in one operation. The countersinking part can be slid up and down the drill part of the tool by means of a hexagon key to suit the depth of hole being drilled.To ensure an accurate fit, it is suggested that the corresponding plug cutter is used from the Faithfull range.Each screwsink is supplied with a hexagon key.Set of 4 Containing sizes 6 (7mm), 8 (8mm), 10 (10mm), and 12 (11.5mm)