The ZooBest filterwool is made from a fine white Polyester fibres which is specially explored for the filtration of water, guarantee maximum filtration for aquaristic use. High crimped and chemically pure, those are the two factors which guarant the highest stability in fresh and seawater. The ZooBest Filterwool can be used as stand alone filter medium or as fine filter at the last layer in a external filter. The ZooBest Filterwool is free of harmful substances, chemical neutral and can be use in freshwater, seawater or garden pond. Made in Germany.the following box sizes are available:Bag with 100 gBag with 250 gBag with 500 gBag with 1000 gSack with 5000 g