Sea-Dog 18 AWG Dark Blue Primary Wire - 500' [8018067]18 AWG Dark Blue Primary Wire 500' Tinned Copper Stranded Wire. Sea Dog Marine Wire is offered in all gauges and colors for primary marine wire applications. All 18 AWG 6 AWG wire is designed and manufactured for marine use with tinned copper wire for corrosion resistance and improved conductivity. The copper is annealed and finely stranded to offer flexibility and resistance to vibration to ensure reliable performance over time. Primary wire is