Even in the same color, they still have difference in detail by year of manufacture.
They take parts in APEL.
Stock Number Reference:
ESS Profile NVG Unit Issue
| Frame Color | NSN | Assign Date |
|---|---|---|
| Olive Drab Green | 4240-01-504-6222 | 2003-02-03 |
| Black | 4240-01-504-5706 | 2003-02-03 |
| Desert Tan | 4240-01-504-5727 | 2003-02-03 |
| Foliage Green | 4240-01-540-5585 | 2006-05-24 |
| Terrain Tan | 4240-01-604-2788 | 2012-04-22 |
Reference: ESS Official NSN List (PDF)（2010-08）