I'm a size 14 and an XL fits perfect for me. In December I used the outer clasps. March of this year I started using the inner clasps. It works great. Each time you wear it you sweat no matter what you do. It helps your stomach sides and back area. Also it doesn't dig into your skin. It covers all the right areas. It has a hole at the bottom so that you can use the bathroom without taking it off. I recommend this product from my own experience.