MasterLine ZipBag is a synthetic bag for fine filter media. With flat shape to maximize the contact area.MasterLine ZipBag+ quick and easy zipper closure+ resistant to acids and hypochlorite+ zipper closure, all made of plastic+ rigid seams to prevent leakage of filter media from the bag+ very fine synthetic material, 250 microns that allows water to circulate easily+ can be reused multiple times+ material is not affected by chlorine or acids+ keeps its flat shape, which helps the water to have a good contact with the entire contents of the bag+ size S - 12x17 cm for about 250 ml of filter media+ size L - 17x22 cm for about 500 ml of filter media