Tokyo Marui Power Down Muzzle Adapter Airsoft.  A great little device that will reduce the FPS (velocity) of your airsoft gun.  Now, you're thinking, why on Earth would I do something like that?  Well, if your gun shoots over a field FPS limit, this is a cheap alternative to getting your mechbox spring reduced.  The muzzle is also great for use in indoor CQB environments where you don't need a high FPS gun.  Some fields require either this or a reduction in your gun to be 'field legal'.  A very popular little device.  Will fit on any Tokyo Marui or clone style AEG on the market.