K2 Filter Media PREMIUM GRADE Moving Bed Biofilm Reactor MBBR. Fresh, Virgin, NOT Recycled. Creates Most Robust Good Bacteria Colonies. Perfect for Aquariums &bull; Ponds &bull; Aquaculture &bull; Hydroponics Aquaponics Aquaculture Hydroponics Ponds Aquarium use 100% PREMIUM QUALITY Virgin Polyethylene 1/2 inch diameter x 3/8 inch width (12.7 mm x 9.525 mm) Colonize beneficial bacterial for hydroponically grown plants Only available from Cz Garden Supply (TM), USPTO and Amazon Brand Registry Protected