Corner Radius Template Metric Large 19-31mm. Cut from fluorescent green material for maximum visibility! 19mm, 22mm, 25mm and 31mm radii. A center hole for each radius aids in perfect snap or rivet placement. These templates make it a snap (no pun intended) to accurately place a snap or rivet at the exact center of the corner radius. Eliminates the need for additional tools to measure and mark these locations.