These replacement parts are for the ProEco BF Series Bio-Flow Gravity Filters. The BF Series gravity flow filters are ideal for large ponds and water gardens. The Bio Flow gravity flow filters deliver crystal clear water with very low maintenance. The filter design uses both biological and mechanical filtration to provide clean, biologically enriched water. A high volume of oxygen is introduced as the water enters the filter, which maximizes the biological filtration process. The foam filter pads create a healthy environment, which supports the beneficial bacteria that complete the biological filtration process and mechanically remove particulate.