The Filtrex CYST Series GreenBlock Filter, FXB20CYST is a specially manufactured carbon filter. It has been made with innovative techniques that help in the absorption of harmful gases and essential contaminants from water. The GreenBlock has been made with high performance carbon block that has more micro pores than other carbon. The filter eliminates harmful gases like the greenhouse gases from the water along with bad taste and odor that is caused by the presence of chlorine. It has a flow rate of 7 gpm and is rated at 1 micron level. The capacity is 160,000 gallons and the dimensions are 4-1/2" x 20".