Made of M42 material (high strength steel & 8% cobalt alloy) which provides high heat resistance & hardened surface for extended life.  These golf club hosel drill bits are a must have shop tool for the DIY enthusiast and professional club building shops alike.  They can be used to ream a hosel to open up a .355 to a .370 and are great for removing debris, burrs, and stuck on epoxy in woods & irons to get the hosel clean & prepped for shaft installation.