Big Boys on light sprung toys "MXZ Sport Models" need heavy springs. Most XP models are delivered with springs for 150 pound riders and that doesn't cut it for most of us USA cheeseburger eaters. These are the "Tug Hill Special" mogul smoothing suspension saving rear torsions you need. Check out our HPG adjustable/rebuildable rear shock package also to really smooth the ride. These fit XP, XS 2008-2017 NON-R Motion skids 120"-137"(MXZ & MXZ Renegades), and come as a pair.