DeadBolt Surge Brake Trailer Lock. Protect your trailer against theft and accidents. Weather grip for easier handling in cold, wet or high-temperature weather. Weather proof lock cylinder for trouble free use. Strong, reversible automotive style key is easy to insert and remove. Double chrome plate for durability and corrosion resistance. Strong, tough one piece machined carbon steel pin. Patented screw and lock security. For surge brake couplers requiring a 1/4 inch pin and a 2-1/2 inch opening.