Top quality Commercial Reverse Osmosis Membrane for a wide variety of applications. 2.5 inches x 21 inches. Options to choose from are the HF4 with 400 GPD or the HR3 with 250 GPD. Produces fresh, clean water. Exceptional performance and results. Is comparable to the Filmtec and Desal brands. Made in USA. We also stock many other filter replacements for most makes and models.