The Billet aluminum Alternator adjusting arm was designed specifically to aid in mounting of certain Alternators with the Hardin Marine LS engine mount rail kit #625-8538. The Billet Arm is satin raw finished and includes a 10MM mounting bolt as well as a lower mounting bolt hardware. This arm was designed to allow for alternator #620-3146 or similar alternator with a mounting span from 6-1/4 to 6-3/4"