ShootingSight sunshades have new UltraBlack interior coatings, for the absolute best anti-reflection properties possible.
Machined parts like lens tubes, and sunshades will black anodize, or oxide treat, interior surfaces to reduce reflections. However, if a surface is smooth enough to provide a specular reflection, anodization or oxide is not good enough to eliminate glare.
The next higher step in quality is to thread the interior, to reduce the area of horizontal surfaces which might reflect. This extra machining costs more, but substantially reduces the glare produced.
The best anti reflection surface is to add a fiber coating to the surface. The random orientation of the fibers further reduces the horizontal surfaces available for reflection, virtually eliminating any glare. This is the highest cost, and highest quality method, as each part needs to be masked and hand coated individually.