Ring Mandrel - Steel Smooth - Sizes 1-15 - Jewelry Making - SFC Tools - 43-078 Perfect for forming and sizing rings from 12.37mm (US size 1) to 23.8mm (US size 15). Has 1/4 size increment markings etched into the side. Smooth all the way around, so it is great for hammering all sorts of metal on, as well as forming wax, PMC, or wire rings. Overall length is 11.38 (29 cm).