A nasal pillow CPAP mask is a type of continuous positive airway pressure (CPAP) mask that covers only the nostrils. This design can be more comfortable for some people than full-face masks, which cover the nose and mouth. The mask has two small, flexible "pillows" that sit at the base of the nostrils, creating a seal and delivering pressurized air to help keep the airway open during sleep. Nasal pillow masks are less bulky and may be less obtrusive for people who sleep on their stomach or side. They are also less likely to cause skin irritation or pressure points as compared to full face or nasal masks.