Why they would make a garment to help a woman "tuck it in" and then make the thigh openings so small and tight is beyond me! They are uncomfortable and would show under any dress or pair of slacks. I had purchased a similar product in a store and was looking for additional items because I liked it so well, but this product (same name as the one I purchased in-store) was a total disappointment. I had purchased 4 and returned them all!
I got the 2x, cause it said that was what fit my measurements was XL --my waist is 35 inches and my hips 45--and I always think it's smarter to go UP one size when it comes to shapewear, especially to avoid muffin top from a waist digging in. Well, I got 2x (went up ONE size), and I wish 3x were available. I could put it on, sure, and sit in it and it was find in terms of hips and upper thighs. But it was snug at the waist and did the bit of muffin-topping thing and at the lower thighs it was a bit too snug, so it pinched in the skin. Which is odd, cause my lower thighs and legs are the slimmer parts, and usually when it fits fine in the hips, the thigh area will be loose or comfortably NOT-snug.
I can still wear it, but I'm one of those who doesn't like shapewear to be very snug. I like to to fit comfortably and even a bit loosely, especially at the waist. If you like to be very snug, then I think going up one size or trying your actual size should be fine. If you have loose skin that can muffin up (I lost 115 lbs, so I do have some loose skin, which is why I like thigh slimmers--cause I have loose inner thigh and lower belly skin), and pinching it in will not look right. Fit is key.
I went to the Maidenform site to see their size guide for Flexees and followed that. You can also go to Bare Necessities and see their guide. I find the Amazon guides are often not very good and I prefer to Google up the actual maker's sites and see their fit suggestions and guides.
In this case, going up one size is still the good general advice for shapewear. :) I'd buy again in a 3x, or just wait until I lose 10 lbs.