Lixada Bicycle Roller Rollers Trainer, Indoor Bike Cycling Roller Rollers Trainer Training Station Exercise Fitness Stand Parabolic rollers with sealed bearing provides stability smooth rolling. Compatible with 24-29inch bike or the distance between shafts within 97-109cm(38.1-42.9in). Fold up easily for storage and transport. Aluminum alloy construction ensures a long time service. Training indoors to develop core strength and improve pedal stroke as well as learn to ride in straight line.