Review on Optical Crystal Photography Prisms Science by Robert Yates

If you expect a "Dark Side of the Moon" spectrum from a triangular prism, you will be disappointed. You need to get a strong light (I used a white LED flashlight) and shine it along the base and you will get a smile in the form of a dense ROYGBIV. I plan to use this as a display (I'm a science teacher). Now to ProMEM. My triangular prism broke when I first received it. I emailed ProMEM (thanks David!) and two days later I had a replacement. Absolutely outstanding customer service. I would definitely recommend the company but make sure you understand what you are getting before you buy!