Includes 21mm, 22mm, 24mm, and 25mm sizes in a 16 piece rack. 16 piece rack has extra storage for existing 8mm - 19mm GearWrench Flex Head Ratcheting Wrenches. The flex head has a spring washer design, which provides continuous head tension. The sleek beam is serrated for the sure grip and the feel for which way it needs to be turned.