This is the 2.0mm Anti Skid Hard Drill Bit, 100mm Length. Unless a bone drill is driven at 90 degrees to the bone surface there is a tendency for the drill to skid over the bone surface placing the hole inappropriately. The anti-skiddrill has a special tip to bite into the bone at virtually any useful angle, accurately predetermining the hole position. Made from hard multi use 420 stainless steel, these are Hard Drill Bits.