The CS ULTRA 4-Pack Refill is a set of high-efficiency air filters designed for ResMed AirSense and AirCurve 10 and 11 devices (used with the CSpring ULTRA adapter). Each filter combines three filtration stages: a carbon pre-filter, H13-grade HEPA core, and a non-woven composite layer to maintain clean airflow during sleep therapy. These filters help remove airborne particles such as allergens, fine dust, and bacteria while also reducing odors and volatile organic compounds. The carbon layer captures larger particles and neutralizes smells, while the HEPA core traps up to 99.95% of particles as small as 0.3 microns. The outer fiber layer catches any final residues before air reaches the CPAP system. Triple-layer filtration means less buildup, fewer blockages, and a more breathable night. Compared to standard filters, the CS ULTRA system offers a larger filtration surface and significantly higher efficiency. Each filter is designed to support airflow up to 100 L/min and should be replaced every 1 to 3 months depending on air quality. This pack does not include the required CSpring ULTRA adapter. CSpring ULTRA adapter required. Replace every 1–3 months, or sooner in dusty environments. Designed as supplemental filtration. Not a medical replacement. Not FDA-cleared; consult your physician before modifying CPAP equipment.