This Attwood Coupler Security Lock provides outstanding peace of mind as it securely locks onto a trailer coupler so the coupler cannot be used. This lock provides maintenance-free trailer security as the lock body is solid brass and the shackle pin is rustproof stainless steel. The shank is 5/8-inch long and it has a ¼-inch diameter. This lock comes with two keys. Attwood Corporation has been an award-winning leader in engineering, testing, and manufacturing the highest quality marine products for over 100 years. We deliver safe and reliable lighting, fuel systems, water systems, seating & pedestals, swim ladders, custom upholstery, and general marine accessories that are easy to install and meet regulatory compliance.