These are super compact Green-dot sights, visible outside in the sun! Low cost price blow-out on these!

Dot has 2 differant size/brightness settings.

The Shot Dot is economical to own and features a green aim dot. Powered by one lithium CR2032 battery, this electronic point sight is compact in design. It has a sleek, low profile that fits both standard and compact air pistols. The green illuminated dot has two brightness settings, is adjustable for windage and elevation, and the projection lens is coated for protection. The built-in adjustable mount on the Shot Dot point sight by Walther fits most accessory rail designs.

These will work on firearms, but they are low end walthers and better suited on a airgun.