IRC 21" Center Metal Valve Heavy Duty Inner Tube | TR-4 Built for demanding applications, this heavy-duty inner tube features a durable center metal valve designed to withstand high-pressure environments and frequent use. The TR-4 specification ensures compatibility with standard 21-inch rim sizes, making it an ideal replacement or upgrade for powersports equipment, agricultural machinery, and industrial vehicles. The reinforced construction resists punctures and wear, while the metal valve provides superior longevity compared to standard rubber alternatives. Trust IRC's engineering for reliable performance in tough conditions.