-CRV carbon steel, this batch of head using CRV carbon steel, batch head surface for steel material color, from inside to outside are the same.-Exquisite workmanship, each edge can be accurately locked screws, and the screwdriver head.-Professional tool to reach tight corners.-Widely used for manual electric screwdriver, screwdriver, drill, air and other tools, ect.-Professional multi size, hexagonal handle on the edge of 1/4 inch. Specifications: Type of shank: 6.5mm/ 1/4 inch hex shankFlexible Extension Bit Shaft Size: 300 x 6.3mm/ 11.8" x 0.25"(L* W)Handle Size: 112 x 6.5mm / 4.