Duro Bicycle Tube 18″ x 1.90″/2.125″ (33mm) Standard American/Valve Review Posted on June 16, 2019 By DuskunkTagged Cycling, Duro, Outdoor Recreation, Sports & Outdoors, Tubes This fits your . Make sure this fits by entering your model number. Bicycle Inner Tube American/Schrader 33mm Valve Fits Most 18 Inch Tires