This is a new in the package 5/8" lock for the 2" receiver (standard size) on your vehicle. This will prevent some low-life from stealing your valuable receiver AND also helps prevent someone from pulling the pin and stealing the whole trailer! This is more and more common! These scumbags pull the pin, drag your truck out of the way, or move the trailer back, and insert the receiver into their vehicle and drive off! This locking pin prevents that, and is near impossible to cut off!
I use this exact lock on my Xterra, and it works great! I've used the other types of locking pins that have the round head, instead of being bent on one end, and they SUCK! What happens is when you go to take the lock part off, the entire thing spins, and you can't get it unlocked! The bent design prevents this! You will receive two keys, and the lock is covered with a cap to keep the dirt out.
This type of cap is MUCH better than the rubber caps, which always fall off!