The mod replaces the simple zoom for weapons without scopes with full iron sights. Instead of using an image, the front and back sight actually line up in the center of the screen laid over the crosshair. There is a new option to remove the crosshair as well.
From the description:
The first playable version of the mod. It should be stable and free of any major glitches, but not every feature is implemented or perfected. Zip file; patch version 1.4