Most corners are 90° which is why most corner guards are 90°. But there are are walls of other angles and the most common are 135° and 45°.
Corners that are 45° especially need protection given that there is less material on the corner due to its small angle. This is why we designed our adjustable angle corner guard.
The additional benefit of using a corner guard with an adjustable angle is that it is able to conform to the wall even if there are slight variations in the angle (e.g. 43 degrees or 47 degrees) due to the construction or movement of the building over time.