Uses a 3D mat to increase the surface area. Kotobuki Craft 3D Mat 45, Set of 3, Target Kotobuki, Triple Box 450 Features: Corrugated 3D mat for increased surface area. Traps debris from breeding water 3D mat distributes water evenly within the filtration tank. It also works great for the growth of filtration bacteria and breaks down water stains. Sizes: Aquarium Supplies, Aqua Supplies, Filter Wood, Wool Mat, For Upper Filter, Kotobuki, 3D Mat, 45, Set of 3, Equipment, Lakic11, ynost88, Kotobuki Crafts, 20110622, TT2, _aqua_maker_kw 4972814531697, 33 3D Mat 45 (For Upper Filter) BUKI