replacing 6V deep cycle marine trailer batteries

I looked again and I see that Costco does indeed list more than one GC2 battery. But all of them are little ATV batteries aside from the one 6 volt I linked and an 8 volt which you can't use. If you walk into Costco and look at the batteries on the rack it should be obvious which one you  are looking for. It will say golf cart on the label and have 3 water fill caps and it will weigh almost twice what the 12v batteries weigh.