The MICHELIN inner tube remains to this day the best quality available on the market, it is thicker than other ranges, and is more resistant to the most extreme stresses. MICHELIN 21UHD Airstop inner tube suitable for tire size: 3.50-21 3.50-21 3.50/21 3.25-21 3.25x21 3.25-21 325x21 325-21 300-21 Non-exhaustive list , consult us in case of doubt