The Kestrel 4000NV has all the same features as the Kestrel 2000 but offers several more features.
The Kestrel 4000NV uses a visible red backlight which helps sustain the user's natural night vision. Includes Wrist and Neck Lanyards, and 2 AAA batteries (included). Also available in an olive drab case. These features make the 4000NV more suitable for field use.
Mini-Catalogs, Issue:03, Page:010
Sinclair, Issue:3B, Page:235