Corrugated tube (K-conduit) is a flexible PVC plastic tube with a ribbed (wrinkled) structure available in 16, 20, 25, 32, 40, 50, 75, and 110 mm diameters. Corrugated tubes are widely used as channels for cables. K-conduits serve as primary protection for cables/wires. They are made of either PVC or halogen-free polypropylene (PP). PP conduits generally have an impact resistance of 750 Nm and are suitable for embedding. It's important to note that a K-conduit with an impact resistance of 320 Nm cannot be used for embedding. PP conduits cannot be used for underground installation; only PVC conduits can be directly buried in the ground. K-conduits are also available with a smooth inner surface and with draw wires. Usually, PP conduits cannot withstand direct sunlight. However, there are PP K-conduits with UV filters, which are black in color.