Designed for use with both short and long action Nucleus & Archimedes receivers in either left or right hand. Made from steel. Designed to be softer than the receiver in order to protect the receiver. Overall length is about 8.5 inches. Hexagonal end fits a 9/16 inch wrench. The wrench must be used with the large lug oriented in the 12 o'clock direction relative to the receiver. Damage to the receiver guide rails may result if inserted in an alternate orientation. Mfg: American Rifle Company