I have a 32 inch waist. I normally wear medium sized undershorts. After reading the reviews, I ordered a pair of medium, and also a pair of large. The large size fit the best. The medium pair tend to ride down in the back when one bends over or sits. I had reservations when I ordered these. I figured they would not look natural. But I thought I would give it a try. I always had women making comments about my great butt throughout my adult life. But sometime after the age of 60 it disappeared. This gives me a butt that looks exactly like the one I lost. Helps keep my pants from sliding down too! Well worth the money.