To include a variety of super thick yarns introduced to the marketplace, the Craft Yarn Council has added a new yarn weight category - Jumbo Yarn Weight #7.
The goal with this change is to make it easier for crocheters and knitters to understand the type of fabric these Jumbo yarns create and the range of hooks and needles generally required.
Also take note that there are slight gauge changes for Super Bulky Yarn Weight #6.
Click on the link to download a copy of this chart for your reference. http://www.craftyarncouncil.com/weight.html