The A. O. Smith Membrane Replacement Reverse Osmosis Under Sink J1 Filter AOS-HERO-S2 is a high-quality water filtration system designed for households looking to purify their tap water. With a focus on reverse osmosis filtration, this under sink filter effectively removes impurities and contaminants to provide clean and safe drinking water. Compatible with AO Smith systems, this filter is a reliable and efficient solution for improving the taste and quality of your tap water.