Application Vortex Razor HD 4000:

The Razor HD 4000 is the essential companion for the extreme hunter, archer and shooter. This highly effective angle-compensated laser rangefinder features four target modes (normal mode, first mode, last mode and extended laser range mode) for any environment.
The HCD (Horizontal Component Distance) mode is intended to be the main mode. The distance displayed is the distance of the horizontal components.

The HCD can be used in the following situations:

• Measure the distance on a flat surface at any distance.
• Measure distances up to 800 meters with a slight tilt
  (less than 15 degrees).
• Measure distances up to a range of 400 meters with a moderate gradient
  (15 to 30 degrees).