Sonic socket bits come in 1/4”, 3/8”, and 1/2” drive sizes. These are Tamper Resistant or IPR bits and include a hole in the center as well as a 5-lobe design. The base for each bit is made from tough and durable Chrome Vanadium steel which fights against corrosion and rust. The bits themselves are made from tool steel for better engagement with the screw or fastener.