X-Formula (XF) is another industry leading innovation from the Bones Wheels factory. X-Formula rolls over rough terrain like softer wheels do, but slides much like a harder wheel will. X-Formula rolls much smoother and faster on all terrains because it absorbs vibration and softens impacts much better than any other wheel in the market. The slide-ability comes from its unique blend of high performance materials. X-Formula will slide when you ask it to, and grip when you need it most.