The Garmin Tacx Galaxia is an advanced roller with a patented swing system which allows it to absorb the forward and backward accelerations from a bike, to keep you from rolling off. When you start to sprint, switch pace fast, or stand on the pedals, this system absorbs the sudden movement, helping you stay upright and on the unit. The roller unit can also be retracted to 80cm for easier, out of the way storage. Specifications: Type of trainer: Roller Roller diameter: 100-110mm Suitable bikes: All bikes with a wheel diameter of 26 to 29 inches Max. footprint: 1350 x 500mm (53 x 19.7in) Height: 135mm (5.31in) Dimensions when folded: 800 x 500 x 135mm (31.5 x 19.7 x 5.31in) Weight: 18.10 lbs Item number: T1100