The tinned copper also resists corrosion adding to the life of the wire.
C.14 Technical Specifications: Conductor - Type III annealed finely stranded tinned copper ASTM B172 Class K Insulation -20 °C to 105 °C flexible, color-coded PVC Voltage Rating - 600-V Resistant to - Acid, Alkali, Abrasion, Flame, Gasoline, Oil and Moisture *Sold as an Individual Built from Type III class K tinned copper, this wire offers excellent flexibility. The jacket makes this 18 AWG marine wire resistant to alkali, abrasion, acid, gas, oil, flame, and moisture. Pacer's marine wire exceeds the requirements and standards of UL, ABYC, and NMMA.