Made of stainless steel, the radius gauge is durable and resistant to rust. This radius gauge has two types of leaves so it can check both convex and concave surfaces. Each leaf is clearly marked, convenient to identify which leaf you need. There are radium gauges of different measuring range that you can choose, used to measure the radius of an object. Very useful gauge for tool & die makers, machinists, and many other worker to check the radius of tool.