I guess its Tarsier eclipse.
Reason for him using it is that
NVGs have distinct inherent limitations. Among those limitations is the ability to only focus at one specific distance, not various distances at the same time. Consider a camera, when focused out on the horizon, images very near become blurry and vice versa. To solve this problem, many soldiers poke small holes in the end of their protective covers. This simple change creates an autofocus effect where the soldier can now see objects both directly in front of him or her as well as all objects out to the horizon.
The limitation of this small hole in front of the lens creates another problem. By decreasing the amount of light entering the NVG, the light sensors cannot amplify the photons enough to create a clear picture for the soldier. This is not an issue when in urban areas with an abundance of ambient light or even on a night with a large amount of moonlight. However, on dark nights or inside building where there is very little light, the NVG image will be very dark and the soldier will not have enough light to see.
Eclipse comes with a internal optical quality camera iris and a dust proof adjustment ring, it allows the soldier the ability to control the amount of light entering their NVGs. By slowly enlarging the iris size, the soldier can increase the amount of light amplified by the NVG, but still retain the autofocus capability.