The Schwalbe Tube No. 19F fits 29" and 29+" (or 28") tires with a width of 54-75 mm and is typically used on mountain bikes, but it also fits trekking bikes. Due to their excellent manufacturing, Schwalbe tubes have proven themselves in the market for years. They are uniform in wall thickness and round in shape. Their precise construction makes them durable at the seam. A comparative test showed that the Schwalbe tube maintains air pressure significantly longer than other tubes (the others lost almost twice as much air pressure as the Schwalbe tube over 30 days). A possible reason for this could be a lower butyl content in the other tubes. The special quality of Schwalbe tubes comes from the uniqueness of their rubber compound. To ensure this high quality, each individual Schwalbe tube is inflated and checked for at least 24 hours before leaving the factory.