The LIF ( Light Interference Filter) is a screw in lens which blocks out IR lasers and illuminators operating at the target wavelength of 1064nm. The LIF also blocks out green lasers. Please note that a LIF will do nothing for IR lasers emitting from 780-940nm.
The Light Interference Filter also acts as a sacrificial lens on your unit. LIFs are threaded into the front threads of night vision goggles or of a night vision monocular. LIFs thread into any monocular or binocular setup that uses PVS-14 objective lenses.
We recommend LIFs when users use visible green lasers in training environments where accidental laser damage could occur.