Motor loc slot style lock and key for your outboard motor. It fits over the toggles on the outboard to keep it secure without a chain. I believe this is the 195mm model, which fits outboard toggles that are less than 165mm across, but I’m not 100% sure of the model number. I have posted measurements, and you can check against your model at the motor loc USA website. This came off a Yamaha 9.9 hp outboard. These cost $114 plus shipping new, I am selling for $50. Has some cosmetic rust, but lock area has been covered by plastic cover and is clean, key turns easily without any issues.