This Reverse Osmosis Membrane element offers 1000 gallon per day with 99.0% rejection and a minimum rejection rate of 98.5%. Designed for light commercial and light industrial use where quality truly matters. The advanced membrane technology and automated fabrication, delivers consistent performance, superb contaminant reduction, and true reliability. OEM Replacement for the commercial PRO-RO-I Series 21" RO Systems. Fits in 4"x 21" light commercial RO membrane housings.