This is an approximately 5,000 foot spool of 18 gauge, UL1430 hook-up wire. The inner conductor consists of stranded 18 AWG copper wire, all pre-tinned together (also known as a top coat). The irradiated, cross-linked PVC insulation is green with a yellow stripe, and provides a great resistance to chemicals, oils, and heat (e.g. the tip of a soldering iron). This hook-up wire is suitable for any general UL1430 application where durability and flexibility are required.