What Size SLEEP ANGEL Will Fit ME Best? The following body weights are given as a guideline to help choose the proper size Sleep Angel: SMALL < 115 pounds MEDIUM - 115 - 245 pounds LARGE > 245 pounds However, since body weight is not necessarily correlated with head size, a more accurate guideline is to have someone measure the circumference of your head with a flexible measuring tape from the chin to the crown of your head (the furthest point from the chin) and back again. If you don't have a flexible tape, use a string to get the measurement, then measure the string. Stated in inches, the following is a more accurate guideline for proper fit: SMALL - 24 ½" or less MEDIUM - 25" to 27 ½" LARGE - 28" or larger Most adults will fit comfortably in a Medium. A common mistake is to assume that a large HAT size equates to a Large size Sleep Angel. Most of the time a Medium is the best fit. The Sleep Angel should fit snugly in order to give needed support to the jaw. Hopefully this will help you choose the size that is right for you.   If you have any additional questions, please feel free to email me at plindorf@gmail.com. Close this window to return to my Ebay listing. Thanks!