These are extra large size screwdriver bits which have a tapered square at one end so they can be used in any piano tuning lever. These screwdriver bits are especially useful in tightening large head screws such as plate screws. Available in either slotted or phillips head style. Bits are 4-1/4" long and are made of tool steel. Slotted bit is 3/8" wide and phillips bit is a size 4.