Sunshade
A tube extension threaded onto a scope's objective that shades the front lens to cut glare and surface mirage when shooting toward bright light.
A sunshade is a hollow tube extension that threads onto the front of a riflescope, projecting the objective lens deeper into shadow. By keeping direct sunlight off the glass, it reduces washout and veiling glare that can wash out the scope image when the shooter is facing toward the sun. The result is better contrast and a cleaner view of the target.
A sunshade also helps tame mirage rising off the objective itself, since shading the front lens limits heat shimmer right at the glass. It does not change the optical correction inside the tube, so it has no effect on parallax; its job is purely to manage stray light at the front of the system.