The Original Adjustable Topaz Chin Strap! SP Medical CPAP Chin Strap available in Std Adjustable & XL Adjustable! This easy-to-use chin strap is the top choice because it is easy to use, has a secure fit and it's COMFORTABLE! No guessing on size with the adjustable with adjustable straps at both the crown of the head and at the base of the neck. This chin strap is great for mouth breathers. The Adjustable chin strap is intended for use by adults to help prevent some of the nasal and oral drying that can occur during Continuous Positive Airway Pressure and bi-level therapy. The 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, reducing or eliminating "mouth breathing" during CPAP therapy. **These products are non-returnable once opened and/or used** Sizing Instructions for Chin Straps You will require a cloth tape measure and an assistant Have the assistant measure1/2 head circumference, follow these 2 steps: 1. Place end of tape measure in middle of chin – have patient hold this end to their chin 2. Measure going toward patient's ear and continue to top middle of head. CHINSTRAP fits ½ head SIZING circumference Small (Small) 10” to 11” Medium (Medium) 11” to 12” Large (Large) 12” to 13” ADJUSTABLE CHINSTRAPS: Topaz STD ADJ 12” to 13” Topaz ADJ XL 14” and above **Chinstraps are non-returnable once opened and/or used***