This Refrigerator Water Filter is used in refrigerators with filter access inside the refrigerator. Simply turn the filter to remove and replace. This NSF® Certified filter reduces cysts, chlorine taste and odor, particulates (class I), lead, and mercury. The contaminants or other substances removed or reduced by this water filter are not necessarily in all users' water. Replace this filter every 6 months to ensure clean, safe drinking water.