The radius gauge is forged with alloy steel and is heat-treated as a whole, which is sturdy and durable. The arc gauge spacing is stacked in an orderly manner, the size is standard, and it has high- measurement. This radius gauge has two types of leaves so it can check both convex and concave surfaces. 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 tools.