This Pentek P-250A under-sink filter set is suitable as a replacement filter set for use with the Pentek US-1000 under-sink chemical and lead filtration system (not included). It reduces the presence of 43 different volatile organic chemicals (VOCs), lead, cysts, mercury, asbestos, methyl tertiary butyl ether (MTBE), and chlorine taste and odor, and has a lifespan of 1,000 gallons. The system meets National Sanitation Foundation/American National Standards Institute (NSF/ANSI) Standard 42 for the reduction of chlorine taste and odor and Particulate Class I, and Standard 53 for the reduction of asbestos, cysts, lead, mercury, turbidity, MTBE, and VOCs. This under-sink filter set is suitable for residential and commercial drinking water filtration. Water filters remove undesirable particles, chemicals, and microorganisms from water by means of a semipermeable barrier, adsorption, or biological processes. They are made of densely packed synthetic or natural fibers that trap suspended particles, materials that block microbes or adsorb unwanted chemicals, or substances that cause a chemical change, such as acid neutralization. For most residential, commercial, and industrial applications, water filters are manufactured in the form of replaceable cartridges that fit inside permanent housings. Filtration systems typically consist of a series of two or more types of filters, each designed to remove different contaminants. The performance of filters is measured by the minimum particle size that is blocked, the percentage of particles or microorganisms that are removed, the downstream concentration of unwanted chemicals, the maximum flow rate, and the amount of water that can be filtered before the filter must be replaced. Water filters are used in a wide range of applications, including drinking water purification, swimming pools, industrial processes, and irrigation, among others. Pentair manufactures industrial, commercial, and residential water filtration components and systems under the Pentek brand. The company, founded in 1966 and headquartered in Schaffhausen, Switzerland, meets International Organization for Standardization (ISO) standards 9001 and 14001 for quality assurance.