SOLOMONE CAVALLI Bicycle Bike Trainer Rollers Foldable for 3 Parts with 2 Step Guards Indoor cycling Dimensions: 51 x 20 inch; Material: steel + aluminum 85mm x 440mm precision machined alloy drums with cartridge bearings provide a smooth and quiet ride. Alloy frame folds down into 3 parts for convenient storage and transport. Durable urethane belt Wheelbase: Adjustable for wheelbase of 970mm to 1090mm. Bearings: Sealed cartridge. Hinge & feet: High impact Resin. Frame: Box Section Steel.