When you purchase wire, it can come on a plastic spool or in a coil. The plastic spool will have a label identifying the wire gauge, item number and other type of information which can be handy when reordering. This is already organized for you and easy to identify. The coils of wire come in a plastic bag or sleeve and have the label affixed on the bag but not on the actual wire. Seems like no big deal until you have dozens of these coils, start losing their bags and they all look the same. The gauge guessing game only works so long!