Tube AUTHOR 20x2.20-2.50. 100% all butyl rubber made with extremely air-tight. Keep air pressure in bicycle tyre longer than cheaper tubes made of syntehtic rubber. American valve 32 mm. Less air loss = having to inflate less. 100% quality control, each AUTHOR tube is individually examined at the factory to ensue air-tightness. ETRTO 50/62-406. # inner tube AVphotogalleryproduct options Photogallery Product options black20x2.20/2.50 = UA#37220001