Triple Square also known as a 'XZN' are commonly found on German vehicles such as BMW Mercedes and Volkswagen. These screws are used in high torque applications such as cylinder head bolts and drive train components. Increasingly triple square screws are found on other European and Asian makes of cars. Other names used for Triple Square screws and drivers are "Double Hex" "Double Allen" and "Aircraft Screws". Despite this "Double Hex" and "Double Allen" are misnomers. The set comes complete with all commonly used sizes from M10 to M18 with the addition of M16H which is tamper-proof. Ideal for a full time mechanic in a busy work shop these bits are for professional use. Specification: Type : Triple Square Socket Bit Set. Drive Size : 1/2". Brand : US Pro Number of Pieces : 5. Socket Material : Chrome Vanadium steel. Bit Material : S2 Steel. Overall Length : 55 mm. Sizes : M10 M12 M14 M18. Tamperproof Sizes : M16H.