From flexible to stiff:
The SCHLAUCH material.

From round to flat
The SCHLAUCH form.
From straight to slightly bent:
The way SCHLAUCH is used.
  Most inner tubes are of butyl rubber. SCHLAUCH’s both flexible and hermetic properties are due to this synthetic rubber. Another factor for the tubes’ consistency is the secret X factor. Whoever wants to become a real bicycle tube, needs additional filler materials for its rubber mixture apart from Butyl - the factor X. Each manufacturer swears by factor X on its own formula. That is why the elasticity and surface of SCHLAUCH always ranges from “much to little“.   If you take a look at cross-sections of different tubes, you will discover all kinds of types – from hosepipe-round to flat as a flounder. Accordingly, there are belts with more or less volume. Long-term studies with SCHLAUCH owners have revealed that belts filled with air lose volume in the course of time.   As you can see on the picture, even bent tubes go perfectly around your hips, since they can perfectly hug to the trousers’ round cut.