A prism should only be one thing and that is a triangular transparent body. It's basically triangular, but the sides (long sides, not ends) aren't flat. Using this as a 90 degree mirror will make the image wavy and fuzzy. Technically it works like a prism, but the educational effect is somewhat lost. The advantage of using a prism as a substitute for a reflector is that the prism can function just as well as a reflector despite being completely transparent. But the upshot with this product is that the prism can serve as a very poor quality reflector which misses the point in my opinion.