The Waterpik IR-30 inline filter has been discontinued. Waterpik is marketing a replacement for the IR-30 -- the IF-35.
However, before purchasing this filter you should note that it does not "screw in" to any existing fittings. You will need to remove any existing fittings and then place the water line in each end of the IF-35. So when you replace this filter you will be replacing the whole unit.