All of our cable is double-insulated UV resistant Solar Cable. We only use corrosion resistant tinned copper making it suitable for marine environments.
If you are unsure of the correct cable size to use please contact us. In general from the solar panel to the solar controller 4 or 6 mm cable is suffice. From the controller to the battery the safest option is to use the thickest cable the solar controller will take and mount the solar controller as close to the batteries as possible to minimise voltage drop.