Air Loc Brand Set of 2 Tire Inner Tubes with TR13 valve stems - 8 inch Combination Size 18x8.50-8, 18x9.50-8, 20x8.00-8, 20x10.00-8 Designed for Lawnmowers/Cub Cadet, ATV, Go Carts Etc. Fits Sizes: 18x8.50-8, 18x9.50-8, 20x8.00-8, 20x10.00-8 Tubes have Standard TR13 valve stem: Straight rubber valve, the most common stem style, measuring approx. 1.38" long and used in the standard size wheel hole of approx. 1/2"