TWO Lawn Mower Tire Inner Tubes for size 18X8.50-8 also fits 18X9.50-8 These are new tire inner tubes that will fit 18X8.50-8 size tires. This same tube will also fit sizes 18X9.50-8 These tubes have the common TR13 straight stem that is made on the tube offset to one side This size tube is very commonly used in the rear tires of riding lawn mowers