All models of bottom bracket sockets are precision CNC machined tools for installation & removal of different external bottom bracket cups. They are made from aluminum billet & anodized red for durable finish & precise fit, that won´t damage aluminum external bottom bracket cups. Knurling on the side of the socket creates better grip when threading cups by h&, meanwhile 1/2˝ square drive makes it easy to use with torque wrenches, ratchets & fixed handles.