Radii on manufacturing drawings specify the curvature of edges or corners, typically measured as the radius of a circle that would form the curve. They are crucial in ensuring parts fit together correctly, reduce stress concentrations, and improve safety and aesthetics. Radii are often applied to sharp corners to eliminate sharp edges that could cause injury, wear, or assembly issues. In manufacturing, these are indicated with a "R" symbol followed by a numerical value (e.g., R5 for a 5mm radius). For example, a rounded corner on a metal bracket may reduce the likelihood of cracks and increase its longevity. Accurately specifying radii helps improve both functionality and the ease of manufacturing, ensuring parts meet their design requirements and function effectively in the final assembly.