I ordered both and L & a 2XL since it's hard to tell with foundation garments. I normally wear an XL in pants but the XL size was too small.  The 2 XL worked beautifully.  This is a very well made garment and very reasonably priced for the quality.  It works well with both strapless and regular bras.and dresses.  Highly recommend it for anyone who is looking for support and shaping for evening wear.  One thing to keep in mind; if the fabric of your dress is light weight or very soft and body hugging the hooks & eyes and seams on the garment might appear as bumps.