Odor-reducing medium carbon filter cartridges are considered suitable for Quiet's Crucial Experts filter to remove odors,water discoloration,impurities and any toxins that may harm your aquarium Easy to use,so you 't have to change the filter 2-4 weeks as suggested by the experts.It is like a charm Because it can filter out anything you 't need or anything that might harm your aquarium and anything in it Aquarium filters are important for your filtration system.Use these filters to help your aquarium and,more importantly,your to last .The filter uses activated carbon to reduce any odor,water discoloration,impurities and any toxins not needed in the aquarium. color:White Material:activated carbon,sponge Package Contents: 6pcs * Filter Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real . The measurement allowed is +/- 1-3cm.