The Faithfull 4 Piece Screw Extractor Kit easily removes even the most damaged and hard to remove screws and bolts. The bits have a self-centring tip and are manufactured from hardened tool steel and double tempered for extra hardness. They will remove screws from wood, metal or plastic, or screws manufactured from any alloy including soft brass and free-spinning screws. Works on the following types of screw and bolts Pozidrive, Phillips, Flat, Hex and Star Headed, even jagged and uneven breaks. They can be used with most power drills. Sizes 1, 2, 3 and 4.