Fluval AquaClear Carbon ensures that significant amounts of beneficial bacteria always remain, resulting in a stress free environment. The carbon improves water clarity ad absorbs odors, discoloration and impurities. Features: Provides optimal mechanical, chemical and biological filtration Includes: 3 Carbon Filters Water Type: Fresh Water & Salt Water Filter Type: Carbon Color: Black Dimension: 4 different sizes to choose from; 3x4.9 oz, 3x2.4 oz, 3x1.9 oz, 9.2 oz) Directions for Use: Remove protective plastic bag and rinse activated carbon insert thoroughly before use. Place activated carbon insert in the middle or top section of the insert basket. Note: Regular filter insert replacement with Fluval AquaClear filter inserts is essential for optimum filter performance.