These are beauties. Made of high quality optical glass prisms. Cube is 20mm x 20mm x 20mm. Great for education. Made up of 4 precision optical glass right angle prisms polarized in such a way that if you send a white light/image thru you'll get outputs in blue, green, and red. Or, you can send in 3 separate images to combine them into one. You can really get creative with this one. New.