All of these made a huge difference to my 28ft RV. Due to the low ground clearance, I had to flip my trailer's axle, but that extra height allowed a lot of back and forth play in my stabilizer bars and jack, even when the wheels were locked. Any movement in the trailer would cause a 1/4-1/2 inch sway as the trailer rocked back and forth on its wheels. Very annoying at night. Structure. This was one of the best purchases I've ever made. The included locks are junk but I had no intention of using them anyway.