This is the replacement nasal pillow cushion seal for the Fisher & Paykel Opus 360 nasal pillow CPAP mask. The nasal pillows are designed to rest under your nose and use the outer rim of the nostril to make a seal. The tip of the pillows will be inserted into the nostril and the outer rim of the pillow uses the outer rim of your nostril to give you a perfect seal. The Opus 360 nasal pillows feature a new smooth contoured shape designed to keep the silicone seal "off the lip" for maximum comfort. Available in small, medium, and large sizes.