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. quality standards. Made of a blend of natural and butyl rubber. Tube Specifications: Valve stem type: TR-4 (straight metal stem (8 mm diameter)). Tire size: 80/100-21M, 90/100-21M, 90/90-21M, 2.75/3.00-21M.