Northern Oceans Combo Carbon is a combination of Lab grade extruded carbon and and regular aquarium hobbie grade carbon for those tanks that dont quite need the extra filtration but need just a bit more than regular carbon can do, with longer life than just regular carbon in your reactor or bag and better filltration flow for those longer times needed between cleaning like while away on vacation or doing a treatment on your tank and need that bit of extra filtration, this is you rperfect choisce for those times or you just need some thing to get you through those longer times.