Kinetic Z Rollers Precision-machined 3.5 x 14.7 inch aluminum rollers (90mm x 374mm) Cri-fold design folds down to just 21 x 20 x 8.8 inches (533mm x 508mm x 234mm) Adjustable to fit bikes with a wheelbase from 38.2 to 43.3 inches (97cm to 110cm) Dual-grooved for left or right-side dismount.Unconditional Lifetime Warranty 3.5 inch roller diameter