Combination tube is also called fuse tube, and features Multiwind liner that's virtually impervious to water ingress.

Special UV-resistant finish assures long life.

Vulcanized fiber tube is manufactured by winding zinc chloride treated  paper on making mandrel to the predetermined wall thickness. 

They are then going through puring, drying, rolling, grinding, and sanding  processes to get desired inside and outside diameters.  Vulcanized fiber tube has a density around 1.40 g/cm3. 

It has good physical properties, mechanical properties, dielectric strength, arc resistance, and arc-quenching characteristics. 

Because of its excellent machinability,vulcanized fiber tube can be sanded, knurled, spirally cut, threaded, lathed, and easily fabricated to various products.

The major applications of vulcanized fiber tubes are fuse cartridges, high voltage cutout fuse liners, lightning   arresters, grommets, insulators, and bushings.