Screwsinks are 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 we suggest you use the corresponding plug cutter from the Faithfull range.Each screwsink is supplied with a hexagon key. FAISSINKS4, 4 Piece: No. 6, 8, 10 and 12.FAISSINKPD, 4 Piece: replacement pilot drills for use with Faithfull No. 6, 8, 10 and 12 Screwsinks. Features: Each size refers to the screw no. it can only be used with Can be adjusted to pre-drill for different lengths of screws Can be adjusted to pre-drill for different lengths of screws To ensure an accurate fit use the equivalent plug cutter from the Faithfull brand Specifications: Dimensions: H:14.0 x W:1.0 x D:7.7 cm Colour: Silver Guarantee:5 years Material: Metal Model Number: FAISSINKS4