This is a 275/300-21, 26/28X3 tube with a TR4 center Metal stem. Recommended application is for Bias Ply tires and the recommended tire fitment is for a 275/300-21 & 26/28x3 tire. Fits 275-300 width, 21 inch diameter tires. This motorcycle tire tube has a TR4 Metal stem and the valve stem location is center. TR4 stem is threaded metal stem 1 inch tall with 5/16 inch diameter. Actual item may differ from photo. Hartford brand tubes are built to meet our specifications using premium grade materials. They are designed specifically for their applications, to provide a high quality inner tube solution and reliable service life. These are excellent quality tubes, available in a wide range of sizes for collector and specialty vehicle applications.