McGard's Prop Lock is a convenient anti-theft device that doesn't have to be removed before entering the water. Its free-spinning collar turns without loosening the lock when attacked by gripping tools. Constructed of naval brass and hardened stainless steel. Once installed, McGard's prop lock offers maximum security for 24 hour protection. Anti-theft device Naval brass and hardened stainless steel construction Maximum security for 24-hour protection Model 74039 fits stern drives: MerCruiser: Alpha 1, Bravo 1 (Including X & XR), TRS OMC Cobra and King Cobra Model 74039 fits outboards: Mercury Bigfoot 40 HP, 50 HP, 60 HP (4 stroke) Mercury/Mariner 70 HP and larger (ex.225 HP 4 stroke before 2005) Johnson/Evinrude 150 HP and larger (2 stroke) Model 74040 fits stern drives: All Yamaha Model 74040 fits outboards: Honda 75 HP and larger Suzuki 40 HP and larger Yamaha 115 HP and larger Johnson/Evinrude 150 HP and larger (4 stroke)