You’re going to need axle extender nuts to put these on many kids bikes. I didn’t have any so I ground down the C channel area where the lock nut would go which ruined the structural integrity of the bar, but had I not done that they seem to be decent enough. Nothing I can’t fix with a welder but these are NOT plug and play for most bikes. Lesson learned is that training wheels kinda suck and to teach your kids on a balance bike or just remove the pedals and lower the seat so they can wobble around.