The mask has Different styles and Size, Choosing a badDifferent styles and Size can cause air leaks, uncomfortable use, Even dangerous to your health，etc .Please compare the size chart to choose the most suitable style and size. Full Face Mask is designed for the user to enjoy a relaxed night's sleep-can be bring you a comfortable night. 360-degree elbow rotation,more comfortable and free. This Full Mask has More venting holes to reduce noise and effectively disperse airflow Description:full face Item Type: Sleep & Snore Model Number: FM1 Pressure Range: 4-20 cmH2O Material: Silica Gel Work Mode: CPAP Type: CPAP Full Face Mask Size: S / M / L Product Type: Sleep & Snoring Certificate: CE FDA ISO Validity: 7-9 Months Function: Patient's Cpap Interface Headgear: Yes User Manual: Yes Package Include: 1x CPAP mask 1x headgear