Works perfectly. I lost a 550lb arm to my system. The part numbers appear to be correct, although the weights are not identical. It works well but I wish it had included a chain and hardware. Without the ability to attach it to a trailer, it's not very useful, and I'm unlikely to damage/weaken the spring arm on my own. I would happily pay a few bucks more to include 10 chain links and a matching U-bolt assembly. -1 star for that.