Use high dense sponge, this aquarium filter pad effectively traps debris and impurities for clear water. The biological cotton filter sponge construction resists acidic condition while maintaining long time filtration efficiency. Measuring 60x50x0.3cm, this black filter pad fits most aquariums systems and works with various filtration setups. Great for fishtank maintenances, also suitable for automotive Air conditioners, air purifiers, and water purification systems. The flexible filter sponge structure allow simple trimming to customizing size and hassle freely when saturated.