Being from the Gulf Coast, I have had a lot of experience with GCF.  The
filters are a roll of toilet paper in a canister less the cardboard roll.
All the applications I have seen have been very effective.  The only down
side I have found is that they are somewhat annoying in winter, as they slow
the flow of fluids passed through them significantly.  If someone could get
the information from them to counter act that, as I have not dealt with GCF
in atleast 3 years and they may have changed their filter media, I would say
that they make a very effective filter system.

-Steve