Product review (4 stars): Good filters But Pricey
These filters come standard on current (past 10 years or so) GE refrigerators with ice makers and/or water dispensers.  You are not required to use one as there is a cap/plug that is sold with each refrigerator to block the filter housing off.  Our water has a less-than-pleasing taste so we use these filters to get as much improvement as possible.  They are effective but very pricey.  You can buy them everywhere but they seem to run $45-$52/each.  I found them on Amazon for less than $40 including Prime shipping.  Still expensive but not quite as bad.  GE has now sold off their appliance and lighting operations to Electrolux of Sweden (Sept. 2014).  They will continue the GE name but it'll be interesting if they do any design changes and make the filters a little less expensive.  There are other manufacturers that offer clones that are cheaper but I've never tried them.