Kinetic Z - Rollersare the perfect option for developing better balance and technique, or for pre race warm-up. Precision machined aluminum rollers and premium bearings provide a smooth, quiet ride. A lightweight aluminum frame folds down for easy transport and storage. Z - Rollers are adjustable to fit bikes with a wheelbase from 38.2 to 43.3 inches (97cm to 110cm). Kinetic backs it up with our Unconditional Lifetime Warranty.