The Winix 113050 Replacement Filter C is a complete one year filter set. The True HEPA Filter captures 99.97% of particles and impurities as small as 0.3 microns, including pollen, mold, dust, pet dander and hair, other allergens and cigarette smoke. The 4-pack Carbon Filters traps large particles, extending the life of the True HEPA filter and absorbs odor in the environment. The genuine Winix Filter C is compatible with Winix Air Purifier units P150 and B151.