I haven't had much use for the prism other than curiosity, having found it as a kid 25-30 years ago. It was acrylic and slightly matt, like car headlights. It came right away in the mail. It's hard glass and much stronger. I used a small AA Maglite to try and get a dark side of the moon style spectrum and that worked. OK. The next day I held it up to direct sunlight from a window and it was emitting a deep bright spectrum. The colors have been beautifully enhanced from red to indigo and purple. I kept it next to my old acrylic and the glass prism definitely worked a lot better. I think as it's glass it gets scratched or broken easily so it comes in a padded storage box with a padded insert. I'm glad I bought it. Pretty cool speaker. Presumably a rectangular prism will also work well and I can jump on it as well.