True-Size Grooved Steel Ring Mandrel: Manufactured with precision, this calibrated, this Grooved Steel Mandrel offers consistent measurements every time. This 13” long mandrel is laser etched in quarter sizes from 1-16.  It is paired to work with the True Size Ring Sizing Sets – using with the ring sizes eliminates the costly errors associated with the sizing of rings that have occurred with other products on the market. Made in USA.