The jacket or sheath physically protects the internal components of a cable, improves the cables appearance, provides flame, mechanical, thermal, chemical and environmental protection to the conductors and components.
Most extruded insulations are also used as jackets. There are some compounds and combinations of compounds used exclusively for jacketing. Often a combination of compounds will be sandwiched together to form a jackets.
Common jacket compounds such as Thermoplastics and Thermosetting include polyvinyl chlorides, polyethylene's, neoprene, CPE, TPR, CSPE, polyurethane, fluorocarbons, Hypalon, Halar, FEP, TFE, Tefzel, EPR, silicones.
Do you have a UL style, a CSA type or an SAE type? If "YES", this should answer most of your questions. If "NO", listed below are some simple questions that should get you to the proper product.
1) What is the approving body? (UL, CSA, CE, SAE, ISO)
2) What is the application? Will there be abrasion, chemicals, oil or flexing?
3) What voltage is required?
4) What temperature is required?
5) Is cost a major concern?
6) What color is required?