Rifle scopes have become far more sophisticated over the years, but the four most basic parts have remained the same. Working from front to back they are:
1. The objective lens (or front lens) is critical to a superior sight picture.
2. The internal erector lenses which right the image.
3. The reticle, often referred to as the crosshair, provides the aiming point.
4. The ocular lens (or eyepiece lens) works with the other lenses to magnify the image, provide correct eye relief, and make diopter corrections.
HOW SCOPES WORK
As light passes through and beyond the objective lens, the resulting upside down image is sent to the internal lenses. Known as erector lenses, these internal lenses return the image to a right-side-up position. Finally, the ocular lens makes a final enlargement of that image and sends it on to your eye. Your Leupold scope was designed, manufactured, and tested to ensure that, when properly mounted and sighted-in on your firearm, you will enjoy exceptional performance. A solid mount is critical to satisfactory performance of your scope.

1 Objective Lens
2 Windage Adjustment
(opposite side of scope)
3 Elevation Adjustment
4 Erector Lenses
5 Power Selector Ring
6 Eyepiece Lock Ring
7 Ocular Lens
8 Eyepiece Assembly
9 Reticle Housing
10 Side Parallax Adjustment