Specifications and Features: Fits all AR15/M16A1 model railing Available in Black or Coyote See through insert 100% die cast metal 1 1/4" in length (3.2cm). This is 3/4" shorter than the other holographic sight Adjust to tighten on and off railing easily No a functional optic. Some fans use a green or red permanent marker to draw a small dot on the lens