Blue Spot Tools 5 Pce Hss Countersink Bits (8-19mm) The Blue Spot Tools 5 PCE HSS Countersink Bits (8-19mm) are manufactured from heat treated carbon steel for increased durability, they feature a titanium nitride coating to maximise the longevity of the bits. The set is ideal for use with power tools and is suitable for drilling in wood, plastics, steel, aluminium, copper and other non-ferrous metals. Manufactured from heat treated Carbon steel with a Titanium Nitride Coating Suitable for hand and power drills Suitable for drilling in wood, plastics, steel, aluminium, copper and other non-ferrous metals.