Minoura RDA80D Rimdrive Trainer Exclusive Rim Drive Action Trainer with magnetic resistance system drives wheel without contacting the tire Ideal for use with knobby MTB tires and for road racers wanting to avoid tire wear 7 resistance levels controlled by smooth and quiet magnetic system; ultra-strong double-wall steel frame Compatible bike wheel sizes from 26 to 27-inches and 700c; can handle up to 264.55 pounds (bike and rider) 1-year warranty for the mag unit; 5-year warranty for the frame