The Saris Mag Trainer features a 5-position adjustment that makes it easy to vary workouts. Simply attach the handlebar-mounted shifter and change resistance during your workout without having to leave your bike. Features: Magnetic resistance unit provides a quiet and frictionless ride Linear resistance boosts workout intensity to match each pedal stroke and gear click Noise level at 20 mph is 70-74 decibels Compatible with quick release hubs; 120mm, 130mm and 135mm. Optional thru-axle adapter available for 12 x 142mm and 12 x 148mm spacing Roller allows for 650b, 700c, 26", 27" and 29" wheel sizes - up to a 2.0 tire Specifications: Resistance: Magnetic Adjustable Resistance: Yes Compatible Wheel Diameters: 650b, 700c, 26", 27" and 29"