Improved thicker design: 1.75" thick. The best biological media available. High Quality, one of the best of all filtration media for Koi pond - Very firm and rigid, sinking. Japanese Filter Mat is extremely inert and easy to service, available in sheet form and can be cut to the desired sizes to fit your filter chamber. Never need to replace. Traps large bits of waste and provides better water flow rate and less chance of clog. Dimensions: 12" x 12" x 1.75"; Package includes: 1 x Japanese filter pad or 6 x Japanese filter pads Dimensions: 12" x 12" x 1.75"; Package includes: 1 x Japanese filter pad or 6 x Japanese filter pads One of the best of all the filtration media for Koi pond - Very firm and rigid, sinking. Japanese Filter Mat is extremely inert and easy to service, available in sheet form, and can be cut to the desired sizes to fit your filter chamber.