I’m now offering three different prisms

Two sizes of Triangular Prisms one is 3 inches long and the other is 6 inches long

Plus

A right angel prism

Triangular Glass Prisms

These triangular equilateral glass prisms are 27mm (1") on 3 sides and come in lengths of 75mm (3")
 They are ideally suited for science lessons used in studying the refraction of the visible light spectrum into prism rainbow colors. Splitting and redirect laser beam.

These right angle prisms can be used differently from standard equilateral prisms. In the image below, the prism on the left is positioned such that it can be used with a laser to demonstrate light reversal based on internal reflection. The prism to the right is positioned such that the side almost facing you could be used with a light source to reflect light up-wards, a simple microscope light source.