Z-MAX 600 zinc plated trailer coupler, 2" ball, fits 3" channel straight tongue, Class III, 5000 lbs. rating with the most popular coupler mechanism ever developed, the Fas-Lok originated as a Fulton brand and is offered in a full line of SAE Class I through IV rated straight tongue stamped couplers. The Fas-Lok latching mechanism allows quick and easy trailer hook-up, and is factory adjusted for convenience. Bolt-On installation.