Marina i110 and i160 Replacement Internal Filter CartridgeReplace every 4 weeks For model i160: do not replace both cartridges at the same time in order to ensure constant presence of beneficial bacteria. Polyester foam traps fine debris; carbon removes pollutants and odors; and zeolite eliminates toxic ammonia Easy to replace Designed to fit the marina i110 and i160 internal filters (a301, a306)