Pilestone
A popular manufacturer of Color Correction Lenses.
Pilestone glasses are much cheaper than EnChroma glasses, but they work in a fundamentally different way. Instead of employing a Notch Filter, they comprise a color tint that can be effective at boosting performance in some Colorblind Tests (e.g. Pseudoisochromatic Plates). However, this type of lens generally does not help in color naming tasks or broad-spectrum Color Discrimination.
Furthermore, many people claim that they give no advantage over even cheaper, simple Magenta-tinted lenses.