These disposable filter cartridges are easy to use and work to help keep your fish tank in tip-top condition. The ultra-activated carbon is designed to remove discoloration, contaminants, and foul odors while the dense, double-sided mesh works to trap debris and fish waste. Features Convenient and easy-to-use. Keeps aquarium water crystal clear. Removes odors and discoloration. Dense dual-sided mesh filters debris and fish waste. Ready to use. 4 Count. Specifications Size: Extra Small. Weight: 0.11 lbs.