I have used off-brand filters a couple times. They simply don't last as long as OEM filters. They are lighter, which means less carbon, which means shorter life. It's simple math. As far as the comments regarding TDS...these don't change TDS. That's not what they do. They remove particulates (which is part of NOT TDS) and trace amounts of chemicals and chlorine, which is NOT reflected with a TDS meter; those levels are too low. Again, pay a little more and buy OEM.