When all you want is to ride your bike and not deal with cleaning road grime off your bike, or worse, succumbing to the elements of winter, the CycleOps Magneto Trainer is the perfect solution. With its simple design and adequate resistance, you'll be ready to take on the spring training rides with a vengeance. The Magneto is designed to fit most common road and mountain bike tires from 26in to 700c, including those with 120mm, 130mm, and 135mm rear wheel spacing. The quick load cam locks the bike into place. You won't need to guess to set the same resistance from ride to ride. The simple design allows you to easily mount your rear wheel in the clamp and then adjust the two inch resistance roller against the tire. The sturdy alloy frame includes asymmetrical rear leveling feet to ensure you're balanced on any surface. A locking ring on the non drive side keeps your bike in place so you're ready to sprint, spin, and climb without wobbles. And, if you travel with your trainer, the Magneto folds for transport. The Magneto features progressive resistance. Essentially, the flywheel is designed so that as you increase pedal speed, the resistance increases. In this manner, your effort and speed follow each other on a linear curve. There is no adjustment knob, you simply shift gears as you would on the road. The magnetic resistance unit is self cooling so that you can ride for hours without sending smoke signals. The CycleOps Magneto Trainer is comes in one size. As stated, it accommodates wheels from 26in to 700c. With an adapter, which is sold separately, you may use a 20 or 24 inch wheel.