The term "4-20x50 SFIR Shooting Gun Scopes" seem to refer to specific types of rifle scope commonly used for shooting sports or hunting. Let's break down what each component of the name represents:
4-20x: This refers to the magnification range of the scope. In this case, it means the scope has a variable magnification that can be adjusted between 4x and 20x. This allows the shooter to zoom in and out to observe targets at different distances.
50: This indicates the objective lens diameter of the scope, measured in millimeters. The objective lens is located at the front of the scope and gathers light to create a clear image. A larger objective lens diameter generally allows more light to enter the scope, resulting in a brighter image.
SFIR: SFIR stands for "Side Focus/Parallax Adjustment." It refers to a feature found in some rifle scopes that allows the shooter to correct for parallax error. Parallax error can cause the reticle (crosshair) to appear shifted when the shooter's eye is not aligned perfectly with the optic axis. The side focus/parallax adjustment helps to eliminate this error, ensuring a more accurate aim.
To summarize, a 4-20x50 SFIR shooting gun scopes are a rifle scope with a variable magnification range from 4x to 20x, a 50mm objective lens diameter, and a side focus/parallax adjustment feature. It is designed to provide clear and precise aiming for shooting sports or hunting purposes.