Crescent Metric Combination Wrenches are made from chrome vanadium alloy steel that has been heat-treated for maximum strength and long-lasting durability They have been coated with a nickel chrome plating and buffed to a mirror polish finish Surface drive® technology on box-end virtually eliminates fastener rounding Sizes have been stamped on both sides for easy identification CCWS1 6 Piece 8 9 10 12 13 & 14mm CCWS3 10 Piece 8 9 10 11 12 13 14 15 17 19mm CCWS5 15 Piece 7 8 9 10 11 12 13 14 15 16 17 18 19 20 & 21mm