The Faithfull 4 Way Chuck Key is a convenient four armed chuck key suitable for use on many electric or cordless drills and bench mounted power tools that are fitted with a keyed chuck of 10 or 13mm capacity. 1 x Key Size: 10 gear teeth, pilot hole 5.2mm. 1 x Key Size: 10 gear teeth, pilot hole 6.8mm. 2 x Key Size: 11 gear teeth, pilot hole 5.8mm.