These tights are decent quality and can't be beat for the price. But, since Amazon doesn't have the manufacturers sizing chart listed I had to guess on the size. So, I ordered what I normally wear, which is a 3-4x. The tights are juuuuust snug enough that I wish that I had ordered a size larger, and according to the sizing chart on the back of the package, that's what I should have done.
It would be wonderful if one day clothing manufacturers would get together and come up with a universal sizing system as to avoid situations like these. But, in the mean time I'd settle for Amazon posting the sizing charts for the clothing that they sell.