HIGH QUALITY 90/90-21 Motorcycle Tube: This 21" Heavy Duty inner tube is the perfect fit for OEM and after-market front tires of most full-size motocross and enduro off-road motorcycles, providing reliable fitment for 90/90-21 or 80/100-21 21" motocross tires (3.00 x 21). HEAVY DUTY 3 MM THICK: Made with 3mm thicken natural rubber, this inner tube is designed to withstand the toughest riding conditions and provide maximum durability. ENHANCED DURABILITY & SAFETY: These inner tubes are engineered to withstand the challenges of rough terrain, featuring advanced pinch and puncture resistance that prevents explosive ruptures and potential harm to both your motorcycle and yourself. They are also expertly molded to prevent pinching, resist twisting, and avoid splitting from the valve stem base, ensuring maximum protection and performance. TR4 VALVE STEM: The TR4 valve stems feature short, straight, and threaded designs that offer both ease and safety during inflation. As a standard valve stem, TR4 is compatible with most hand pumps, making it easy to find a suitable pump for your needs. These heavy-duty valve stems are also firmly seated in the tubes via vulcanization, ensuring maximum stability and reliability. FOR OFF-ROAD & MOTOCROSS TIRES: For dirt bikes, off-road motorcycles, and motocross motorcycles, heavy-duty inner tubes are a must for optimal comfort and protection. These specially designed tubes can handle even the most challenging terrains, offering the best and most cost-effective replacement option. With superior durability and resilience, these tubes are the perfect fit for off-road and motocross tires, giving riders the peace of mind they need to tackle any track with confidence. FREE-REPLACEMENT WARRANTY: Scan QR code on product box to register your FREE 6-MONTH replacement warranty (Just pay S/H)