Bridgestone – Bridgestone Tubes, including TR4 heavy duty motorcycle tubes, PV78 scooter tubes, off-road sizes such as 80/100-21 and 70/100-19 and street fitments from 2.50-18 to 140/90-15, covers the part of a wheel nobody thinks about until it fails. On any spoked wheel the tube is doing real work: it holds pressure against a rim strip and spoke nipples, it flexes constantly with the casing, and on a dirt bike it takes direct hits from rocks and rim pinch on hard landings. Bridgestone's TR4 tubes use a thick, uniform butyl wall with a properly bonded stem, which is what prevents the slow leaks and stem tears that low-grade tubes develop, while PV78 straight-stem tubes suit small scooter wheels. Correct sizing matters as much as quality, because an undersized tube stretches thin and an oversized one folds and chafes. Sizes here span 10 through 21 inch rims for motocross, trail, dual sport, cruiser and scooter wheels, so you can match the tube to the tire you are mounting. Replacing the tube with every tire change is inexpensive insurance compared to sorting out a flat on the trail or on the shoulder of a highway.