The best way to know which size Waist Trimmer will fit you is to find out your waist measurement. If you have access to a tape measure, measure your waist below your chest and above your belly button. Below is our sizing chart for the Original Waist Trimmers (Original, Neon Series, and Matte Series): Small: 35" length x 8" width -- Recommended for waist up to 33" Medium: 41" length x 8" width -- Recommended for waist up to 38" Large: 44" length x 9" width -- Recommended for waist up to 40" X-Large: 51" length x 10" width -- Recommended for waist up to 49" XX-Large: 60" length x 10" width -- Recommended for waist up to 58" We want to ensure you receive the best fit, so feel free to reach out to our team directly with your height, weight, and pant/dress size (numerical) and we’ll be more than happy to talk you through picking the right size for you!