Radius gauge set (bend diamater ruler), metric

A set of rulers for measuring different radii. Each ruler includes a small hole for threading them together into a single bundle. Here with diameters 4, 5, 6, 8, 10, 12, 15, 20 and 25mm. The convex shapes (outer radii) form a 180° arc (creating half-circle profiles). The concave shapes (inner radii) form 90° arcs (quarter circles), with tangential legs extending beyond the arc to create a right angle. "Main" refers to the rulers with letters engraved (depth of 0.4 mm). "Letters" refers to the inlays intended to optionally fill the engravings with a contrasting color.