The filter holder bags that came with all my lens filters are a bit too big to fit into the foam of my hard case, aside from too many things in there already. Some are double-bagged and not easy to find. So I made my own that holds four per slide, and I can see what they are too. Specs: About 2 3/16" wide and 5 1/4" tall with the 1/4" double fold edge binding from the fabric shop (All stuff was from there for this project.). Heavy vinyl was formed over the aluminum piece I fabbed up due to the heat although wood might be used. The semi-round piece is about 1/4" thick and a little larger than the filter diameters of 1 1/4". I couldn't get the flat vinyl to conform without using heat so I used a heat gun at 650 degrees and heated the vinyl up over the aluminum piece (Clothespins were to hold it down and not to blow away, plus when hot enough they move inwards a bit.). Once hot and formed over the piece, I slapped the cold water wooden piece that conforms to the aluminum part over it quickly and then threw the entire thing into the ice water to harden and hold its shape. Then temp glue them with flexible vinyl glue (or RTV) to the heavy-weight non-fusible material (fabric shop again), temporarily sew them in place once dried (I used a circular edge on the bottoms so they slide better than square edge), and then finish the entire edge with the 1/4" wide double-fold binding tape. Done.