Fulton 72783 Universal Trailer Coupler Lock The Fulton Universal Trailer Coupler Lock is designed to prevent theft and keep your trailer secure. The bright yellow color is highly visible and deters thieves. This coupler lock features a ratchet design with six locking positions for versatility. Designed to fit 1-78, 2, and 2-516 trailer couplers. Features Guards against trailer towaway theft Fits Most 1-78, 2 and 2-516 Trailer Couplers Distance between lock shackle holes center to center is 4-12