On our Keystone Fuzion 429, the underside of the large slide-out (the one with the fridge, stove, and couch) was getting damaged each time we put it in or out. On this slide-out, the underside has a DARCO material that helps the slide-out slide over the threshold. No rollers to help. We installed a pair of "BLK SLD-OUT REPAIR PANEL" that we purchased form a Lazy Days RV. The tech that fixes slide-outs recommended this as a solution.