18" x 1.50 - 2.125" Bicycle Inner Tube w/ Schrader Valve (Pair). Schrader Valve. - Schrader valve. 18" x 1.50 - 2.125" Bicycle Inner Tube (Pair). - Welded butyl inner tubes. This inner tube represents great value for money and are manufactured from high quality butyl rubber.They feature a durable air tight welded butyl rubber construction a nd are designed to 18" wheels.