Martin Wheel 18X850/950-8 20X800-8 TR13 Inner Tube for Lawn Mower This quality butyl rubber inner tube fits tire sizes 18X850-8, 18950-8, and 20X800-8 Use: Lawn & Garden, Utility, ATV Fits tire sizes: (18X850-8), (18X950-8), (20X800-8) Valve stem type: straight (TR-13)