So let's get to the point shall we?
This scope is mostly made for looks, but it works to a certain capacity, since if you are looking through the scope at an angle, you will not be able to see through it all that easily, but if you are looking straight through it, you will be able to see your target quite clearly.
Though not directly based on anything (it does resemble the generic red dot sight found on the M4A1 and G36C in Call of Duty 4's single player campaign, however), it still looks convincingly realistic.
To build your own, here's what you will need:
*yellow = x3
*green/black = x1
*Y-clip = x4
*dark blue 7 clip (circle with space missing) = x10
*light blue ring = x3
Gear Thingies Or Whatever:
light gray closed = x2
dark gray open = x1
Step 1: Lineup
I apologize about the blurry photos, I was in a hurry.
Note: I used some silvery blue parts instead of some of the dark blue ones. Ignore this.