1 = Commercial grade oils, mass produced specifically for the fragrance and flavor industries
2 thru 6 = Higher quality than commercial with better odor properties, pesticide free according to GC/MS analysis. All numbers within this range are generally equivalent in terms of therapeutic quality but not necessarily in terms of odor quality. Generally, let cost be your guide for quality. The higher the price the better the quality.
PLEASE READ: In the 2 thru 6 range a higher number does not necessarily mean better quality. In fact, sometimes a lower number will be a higher quality oil. As with most things in life price is your guide to quality, you don't get a Cadillac for the price of a Chevy!
7 = Oils certified at the farm level.
9 = Wild Crafted - naturally growing in the wild, not cultivated.