This listing is for the cuff sleeve chemise top only. This is a baggy tube top style chemise that can be worn under a bodice, corset, or waist cincher... The top has elastic to hold it up. The Sleeve cuffs have elastic and are attached to the top under the arm.
You would take your actual Bust measurement and add 4-6" for a proper baggy style fit.
(example: Your fullest bust measurement is 46", you would choose size XL - 50")Size Chart