Designed specifically for Yamaha lower units, this set features a stainless steel locking bolt. Simply replace one of the original bolts above the propeller with a McGard locking bolt. Once installed, the lower unit lock bolt offers 24 hour protection. Constructed of through-hardened stainless steel for maximum security. A free-spinning collar will turn if attacked by gripping tools without loosening the lock to avoid costly theft. For maximum security, use the Yamaha lower unit lock bolt in conjunction with a McGard outboard motor lock.. 3.22" overall length. M10 x 1.25 thread size. 5/8" hex size. Set includes lock bolt and key