This LED Illuminator Module allows shooters to use a Small Arms Collimator in low/no-light conditions by backlighting the reticle. It emits a dim, red light, which minimizes signature and allows for use with unaided vision or NVGs. To prevent unitended discharge (and downrange signature), it is only activated when the module is screwed completely into it's position at the back of the optical tube. It includes a stainless steel lanyards and a ferrule so that it can be attached to the collimator body (you'll need a crimping tool of some sort).
This LED Illumination Module is a direct replacement for the USMC Infantry Weapon Collimator (IWC), the US Army Sniper Weapon Collimator, and most other collimator models.