This easy-to-use chin strap is the top choice because it is easy to use, has a secure fit and its COMFORTABLE! No guessing on sizes because it is adjustable. A snug and secure design ensures that the patients chin will be held in place while the patient sleeps. Features: Adjustable straps at both the crown of the head and at the base of the neckThis chin strap is great for mouth breathers.Soft Breathe-O-Prene straps and improved velcro fasteningsUltra-wide strap constructionPlease note: The adjustable chin strap is recommended for adults to help prevent some of the nasal and oral drying that can occur during CPAP and bi-level therapy. The Adjustable chin strap helps to prevent air flow leaking from your mouth by holding your chin in a stable position which encourages breathing through your nose. Many patients who use a nasal mask require a chin strap to assist in keeping the mouth closed. Sizing Information: The Topaz Adjustable Chinstrap is available in two sizes Standard and Extra Large. Standard Topaz chinstrap adjusts to a maximum size of approximately 22-25 inches.Extra Large Topaz chinstrap adjusts to a maximum size of approximately 26-28 inches.