ContiTPU tubes feature the highest grade of micron-thick TPU that is deployed into seven sealed layers to maximize airtightness and durability. The tubes are uncolored to further ensure the avoid air retention issues caused by dye-related surface imperfections. Each ContiTPU tube is post-production quality checked. The base of the valve stem is slightly tapered to improve fit to the wheel rim and reduce unwanted movement, while the valve is internally threaded to allow the use of valve extensions or a valve core. replacement. ContiTPU tubes feature the highest grade of micron-thick TPU that is deployed into seven sealed layers to maximize airtightness and durability. The tubes are uncolored to further ensure the avoid air retention issues caused by dye-related surface imperfections. Each ContiTPU tube is post-production quality checked. The base of the valve stem is slightly tapered to improve fit to the wheel rim and reduce unwanted movement, while the valve is internally threaded to allow the use of valve extensions or a valve core. replacement. ContiTPU tubes feature the highest grade of micron-thick TPU that is deployed into seven sealed layers to maximize airtightness and durability. The tubes are uncolored to further ensure the avoid air retention issues caused by dye-related surface imperfections. Each ContiTPU tube is post-production quality checked. The base of the valve stem is slightly tapered to improve fit to the wheel rim and reduce unwanted movement, while the valve is internally threaded to allow the use of valve extensions or a valve core. replacement.