This is a general purpose blue fluorescent filter cube with a dichroic mirror at 510nm. It will fit the Nikon Eclipse series of fluorescent microscopes, such as E400/600/800  and TE200/300 Inverted microscope. It is in the catalog with a product number of 81746 or MBE64040. The cube is in new condition and still in its' original packing. Thank you for looking!