Review on Right Angle Prism Set Hypotenuse by Ray Richards

They are well made and polished and usually get five stars. However, they do get two stars: one for simply tossing them into separate plastic cases and then combining them into one larger plastic case; another star for acrylic, although this is not stated anywhere in the product description ("index of refraction close to optical glass" might be a clue); as a result, they do not have a truly flat "optical" surface, and very slight continuous irregularities are evident in transferred images.