Shooting or the use of optical equipment with a NBC - mask with centre filter is always a problem.
Our undivided knee enables the bearer to swing the filter either to the right or left side without disconnecting the filter and it stays in the decided position.
100% tight while swinging!
No reduction of the airflow!
The weight of the filter stays in the centre of the mask.
Changing the position of the filter is always possible.
Fits to any mask with NATO-standard thread.