Underwriter Laboratories has set the standards for product safety and has a through certification process. Mueller Electric is proud to provide UL Listed items and this blog post will provide some insight into what it means for something to be UL listed.
There are many varieties of wire and cable insulation suited to a variety of needs. Insulation is made of a non-conductive material that surrounds the wire and will resist an electric current. Keep in mind that The thickness of the insulation determines the voltage rating. You can get high voltage from any kind of insulation depending on the thickness.