Suppressor

A suppressor, or more popularly known as the silencer, is a device attached to a firearm's barrel to reduce the amount of noise, flash, and recoil generated by the firing of the weapon.

It takes the form of a cylindrical metal tube that is fit onto the firearm's barrel, with various internal mechanisms to significantly decrease muzzle flash and recoil, giving the weapon a barely noticeable sound, and increasing stealth applications.

The M7S Submachine Gun, a variant of the M7, features a suppressor attachment.

Trivia

 * The original plan for the suppressor, which was during World War II, was to modify the sound of the weapon firing into a different, unrecognizable sound, rather than to "silence" the weapon.
 * It is unknown if the suppressor is attached to any other UNSC weapons, such as the SRS sniper series, or if the Covenant have a counterpart of this attachment.