The lenses in the Sirmont are made from nylon, which is a lightweight material that can be made in many tint color options.
Choosing the right lens for you:
Grey Lenses are the most neutral option, as they control the brightness of light without affecting color perception, but do not provide the contrast of green or brown lenses.
Green Lenses provide a balance between the color neutrality of grey lenses and the high-contrast provided by brown lenses.
Brown Lenses are excellent for providing contrast and reducing brightness at the expense of not having a color neutral tint.