Wald W10252 Bicycle Training Wheels (16 to 20-Inch Wheels.75 and 1-Inch Frame Tubes) For SINGLE SPEED BIKES: Features 5 1/2" diameter plated steel wheels with rubber tires. Intended for use by riders weighing up to 100 pounds. The new frame adapters enable this wheel set to be mounted on bicycles with .75 and 1.00-inch rear frame tubes The training wheels can also be mounted onto bicycles with 1.25-inch rear frame tubes when the frame adapters are not used. Easy to install. To fit properly there must be at least 3/8" of axle outside the axle nut on both sides of the rear wheel. Wald training wheels are designed exclusively for single-speed bicycles, not designed for multi-speed bicycles.