4" long drivers in chrome plated holders in sizes XZN4-XZN18 XZN16 & XZN18 drivers have tamper proof hole for application on VW and Porsche brake calipers Standard length drivers in sizes XZN4-XZN18 Sizes 14,16,18 are tamperproof 1/4", 3/8" or 1/2" drives S2 alloy steel bits, heat treated to RC 60/63