Thanks to their unusual shape, these reels offer a number of advantages: More grip and slide control Less friction - more speed Better traction on a wide range of terrain Best roller for rough surfaces Brand new DNA formula. Fast, soft and superior grip. Best wheel in the world over rough terrain (pebbles, debris, sand, water, etc). Made in USA Diameter: 72mm Hardness: 78a Bearing seat: Centerset Scope of delivery: 4 rolls.