Set includes six measuring heads for measurement of surface radii ranging from 2.5mm to 1000mm. The smallest sample diameter that can be tested is a 4mm convex or an 8mm concave. Seven standards are included: two spheres (radius 3mm and 5mm), five plates (radius ranging from 10mm to plane for convex surfaces and -10mm to -200mm for concave surfaces). The radius is a function of the size of the measuring head used and the dial gauge reading. Tables are included to allow for quick determination of the radius.