Nasal BASIC masks seal around your nose in the shape of a triangle and are held in place by a four point headgear. They do not seal over your mouth. Nasal BASIC masks are the original type of CPAP mask and remain the most popular. They come in silicone,gel or cloth styles. Avoid low end nasal BASIC masks as the comfort gap between high and low quality nasal BASIC masks is large. Size: 79±8（L） 63±8(W) 52±5(H)