Product review (5 stars): Dead Simple Replacement
A no brainer for sure, but there are instructions.  Line up the arrows and twist on.  No need to worry about the water supply being shut off.  Run your water dispenser for about 3 minutes and you are good to go.  Not cheap though...I imagine they are still paying off the patent.  By the time the patent expires they will have a new design...nice racket.  Still, it is worth it to have nice clean water and ice cubes.