RUBENA Extreme Tube. Enduro / Downhill / E-Bike – Designed for downhill / enduro / E-Bike – Wall thickness 1.2 mm. EXTREME Butyl tubes have a reinforced 1.2mm thick wall and are designed for riding in challenging endurance or downhill / enduro conditions, and for the special requeriments of the new E-Bikes or heavy weight bikes (Fat / Plus…)