A Neuralyzer is a top secret device used by the Men in Black to wipe the mind of anyone who sees it's flash, with dials that set the amount of memory to be erased, one for hours, one for days, one for months, and one for years, after which they are in a trance you can use to supply memories to them through simple explanation. Paired together with this you also get a snazzy pair of sunglasses which deflect the light created by the Neuralyzer to avoid being harmed by the effects.