This review is to help anyone out trying to figure out what size to get.
I am 5'3 140 to 145 lbs and my waist size under my ribs (smallest radius) is 38 inches. I bought the xlarge and it fits snugly.
I started wearing this yesterday on the first hoops (largest). Today I am trying the mid loops and it's feeling pretty snug still, so that's good.
Tomorrow I'll see if I can try the tightest loops.
I'll try and make it back on here to follow up.
Hope this helps!