All I can say is that they work. I'm happy with the price, we have a 38ft RV with two slides. It would rock front and back. would drive me crazy My son has a Fitwheeler and paid 3x for the set he has. Its steel is a bit heavier and you have to be careful not to get your hand caught when locking it. These thin ones were cheaper in price. Don't worry about pinching your fingers or hand. We parked the RV, winterized it, and I left them, thinking they would rust over the winter. They still look like new and work very well. The only thing I didn't need to do was that I had anti-slip tape. I put one by one where they meet with hoops. I used them without them and they didn't move. For the price I am very satisfied. go buy them again For the price it's worth it.