Size:PH1* Bits made of S2 alloy steel for superior hardness and great rust resistance.* Chrome vanadium steel socket for high strength and superior torque.* Notched drive ends fit any 3/8-inch drive ratchet or extension, preventing them from falling off.* It features a radius corner design, causing the socket to grab the sturdy wall of the fastener instead of grabbing the corners, resulting in less wear on the fastener.* Wide application in DIY hand-making, household maintenance, and most general repairs.