This is replacement media to refill the Whole House Water Filter 2-Media 1-Tank Filter for CHLORINE.  (If you have chloramine, see that separate item.)

The choice you have is the option between raw media or a filled tank.  A filled tank is recommended for most people.

With raw media you need to remove the existing media and replace it with the new. This is awkward, as the tank opening is small.  It can take some time.  This option is available, but not recommended for  most people.

Otherwise, you can get a complete, full, filled replacement tank. With that option you just disconnect the older tank and attach the new one.

This filter media should be changed every 600,000 gallons as of early 2017.  Earlier models lasted less long – most at 350,000 gallons.  Follow original instructions.  This refill has been upgraded and now can go 600,000 gallons before changing again.

The media included is both the patent-processed FOAM ADVANTAGE kdf and the granulated coconut carbon.

You may have a blue tank or one that looks like the cutaway picture. This is the right media in either case.

This whole house water filter replacement or refill does not include replacement filters for sediment pre-filters.  Those normally are changed once a year.  Purchase separately.