ETA: These now state that they are “dry,” which means that they have a much longer shelf life. Good to know, since I prefer to be able to store a spare, since our well water tests as undrinkable without filtration to remove some of the substances that would make us sick if we drank it. We’ve used several of these now and they’ve worked well.
Original review: Not much you can say about this membrane, except that it works great. It fits our iSpring RO unit and seems to do its job just fine. Don't buy these too far in advance, as they do have a shelf-life.