This item is currently out of stock.
This RV Designer lock pin slides through the coupler latch to keep it from popping open while you're on the road. It's a straightforward metal pin, sized at 5/16" x 2-9/16", made to fit standard coupler latch holes.
Worth keeping a spare in the tow vehicle - it's a small, easy-to-lose part that plays a real role in keeping the coupler locked down.
Check that the pin is fully seated through the latch before towing, and replace it if it's bent or worn.