I purchased the 12 foot long 4 gauge 100% copper jumper cables. Actual conductor is definitely 4 gauge. The parrot clamps are very high quality and the wire to copper jaw connection is done very well. The insulation is thick and quite flexible. For the price paid, this is easily one of the best jumper cable values to be found. By the way, I nerd things to death and looked at 50+ pairs of jumper cables before I decided on these.