Heavy duty wool mat that will last long even in large tanks. Gex Value Pack of 6 Filtration Mats 2 Targets Upper Filter (Both Freshwater and Saltwater) Features: This wool mat is used as physical filtration for the upper filter. Removes suspended objects such as leftover bait and droppings and small debris to get clean water For use with a typical 23.6 inch (60 cm) aquarium, but can also be used for small filtration filters. Contents: 6 pieces x 2 pieces. Depending on the type of filler material, this product is made of regular type filler material, and if the flow rate is noticeably dropped, it may cause clogging. If you feel the circulation of your breeding water has been poor, please check the stains on the wool mat. If the dirt is heavy, replace it. Check the case when you open the case when you clean the filter and replace it if the mat is quite thin. Even with high performance filters and filler materials, the wool mat will not retain turbidity or debris over time. While this is durable, wool mats are consumables. Replace it regularly when it gets old. Size (approx.): 15.0 x 4.7 inches (38 x 12