During CPAP therapy, the mask's seal is among the most important factors. Each mask should provide maximum comfort while also forming a seal that won't allow air to escape. This is why cushions are so important. Unfortunately, consistent use leads to creases, oil accumulation, and other issues that cause the seal to fail. Because of this, you should replace the cushion at regular intervals for maximum effectiveness. The Mirage Quattro's cushion uses a basic clip that makes installation or removal simple. By signing up for our Sleep Club Subscription, you can eliminate the hassle of frequently ordering replacement cushions and other equipment. We send you the replacement parts you need when you need them, mailing them directly to your door.