The Durston Square Ring Mandrel ranges in size from 4mm to 10mm and is made from hardened steel, induction hardened to 64 RC.The mandrel is unmarked, ground and polished to ensure long lasting durability and precision. Designed for precise shaping and adjusting of square ring shapes, this mandrel offers reliable performance for the professional jeweler in the studio or factory. Weighing approximately 100 grams, it will last for years in demanding work environments.