All bottom bracket socket models are precision CNC-machined tools for installing and removing a variety of external bottom bracket cups. They're made of aluminum and anodized red for a durable finish and precise fit that won't damage aluminum external bottom bracket cups. Knurling on the side of the socket provides a better grip when hand-tightening, and the 3/8˝ socket facilitates the use of torque wrenches, ratchets, and knobs.