Question: what is the difference between 4 gauge and 6 gauge battery cables?
Answer: It has an external insulation rated to 600 volts. Cable size is standardized by it's AWG number (American Wire Gauge). The higher the AWG number the smaller diameter the cable, i.g. 6 AWG is smaller than 4 AWG. All cables smaller than 1 AWG are called "gauge", i.g. "I need 6 gauge cable".