This 10" x 2 1/2" CR1 carbon cartridge is perfect as a third stage carbon filter in most 5 stage home RO systems. 0.5 micron and made in USA.
This Filter Cartridge is only needed in a 5 stage system that has 3 filter housings before the RO Membrane.
Please note in these strange times with supply chain issues we may substitute this Carbon Block cartridge to another manufacturer with an identical or better rating.