The RPM nerf bar eliminates the stock hook-over-the-chassis that supports the nerf bar and replaced it with a structural cross rib running parallel to the chassis for optimum rigidity and anti-Blue Nerf Barsdeformation characteristics. By eliminating the hook, installation is easier; the nerf bar doesn't have to be deformed to get it in position and the nerf bar no longer pulls on the side of the chassis when it takes a hit.We also switched to a full round radius in the compression area of the nerf bar. The stock trapezoidal shape forces too much impact energy into the tiny corner radii near the body support area, usually ending in a break. The RPM nerf bars full corner radii are huge in comparison and allow a progressive compression of the nerf bar while distributing the impact energy over a much larger area, preventing breakage by design.Our design element changes, coupled with the best impact absorbing material in the R/C industry, make RPM nerf bars the best Slash and Slash 4x4 nerf bars available!