This is the replacement Nasal Cushion for the ResMed N30 Mask. It is available in Small, Medium and Small-Wide. The unique under-nose cradle design allows for a comfortable and effective seal without any of the nostril soreness or irritation at the bridge of your nose. It is a truly unique design and fit. The replacement cushions are color coded to help determine the size: Blue is Medium, Red is Small, and Purple is Small-Wide.