Review on 📸 Exploring the Spectrum: Triangular Photography Experiments for Teaching by Sean Davis

Looks like they were roughly cut from a long piece of extruded glass. The finished edges are straight but the ends are not square. do not line up in a vertical position. Also, I assumed 1.97 inches referred to the finished face (they look square in the photo), but that's just the length. The width (which is the most important part) is only one inch. Came in a nice box, I will not buy again.