Recently Rockler introduced a set of acrylic radius gauges. This set of six gauges can be used for reference while turning, checking the radius when you’re rounding edges, measuring moldings you want to duplicate, or any other task that requires precisely radiused curves.
The six laser-cut acrylic gauges measure 12 different radii: 1/8″, 1/4″, 3/8″, 1/2″, 5/8″, 3/4″, 7/8″, 1″, 1-1/4″, 1-1/2″, 1-3/4″, and 2″. Each gauge measures both concave and convex arcs for two different radii.
Rockler charges $20 for this set of six radius gauges.
Radius Gauge Set [Rockler]