Dual Drive bits are a unique stubby length fastener driver system that can be used with any 1/4 in. square drive socket spinner handle, ratchet or T-handle and drive the outer diameter with either 7/16 in. wrench or box wrench (12 mm and 13 mm tip driven on od by 1/2 in. or 13 mm wrench). Bits made from S2 tool steel with proprietary heat treat for superior strength and durability. Precision tip profile manufactured for positive and precise fastener engagement. Titanium nitride coating for added strength and wear resistance. HEX METRIC set includes 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, 12 mm and 13 mm. Comes with color coded storage rail.