The best protection available against expensive stern drive theft. Simply replace one of the stern drive mounting nuts with a McGard lock. These stern drive locks are fully machined from high quality stainless steel and are through-hardened. This proven design features a free-spinning collar that turns if attacked by gripping tools without loosening the lock. Fits the following twin drives: MerCruiser III SSM, IV SSM, V SSM, VI SSM, NXT. This product may contain globally sourced materials/components.