This 8-Level Resistance Indoor Bike Trainer is made of solid steel and adopts a pyramid structure design to ensure its stability. The eight adjustable resistance levels allow you to choose the difficulty that's right for you. The nylon feet effectively protect the floor and increase the friction of the bicycle training frame so that it does not shake. This bike trainer is suitable for 26'', 27'', and 28'' tires, and the folding design makes it easy to store.