IRC Heavy Duty Tube (80/100-21) IRC Heavy Duty tubes are designed and constructed to offer great performance in the most extreme motorcycle riding conditions. IRC heavy duty tubes are made 3 mm thick and puncture resistant, making them durable to better handle extreme and aggressive use. For maximum performance and durability, IRC tubes are made of a blend of both natural and butyl rubber. Heavy duty tubes are 3 mm thick and puncture resistant. High quality Japanese tubes meet or exceed O.E.M.