This is the direct replacement for the Confidence Gauge included in the USMC Infantry Weapon Collimator kit. It is compatible with most M4/ M16 collimators calibrated for 100m zero distance.
P/N: 4500-0016
NSN: 4931-01642-3513
Collimator kits come with a confidence gauge that is used to ensure that the collimator remains accurately calibrated. It can be used at routine intervals (i.e. one time annually) or any time the collimator is dropped, bumped, etc.