The Chanson Water C3 pre-filter is the ultimate in water filtration technology. There is not an ionizer filter on the market that can compete with this triple- canister filtered water. Each C3 canister is devoted to removing harmful chemicals, heavy metals, flouride, chlorine and over 100 additional contaminants. The C3 regular filter is for under the counter ionizers. The C-MUC is for all brands countertop ionizers with filter installed under the sink. The C3-C is for installation on top of counter with countertop ionizer.