This is a skin for the Custom SMG item. You will be able to apply this skin when you craft the item in game.
The Custom SMG is a quick-firing, low damage submachine gun with moderate recoil. Its moderate spread and low bullet velocity limit the use of the weapon to close and possibly moderate ranges, but its maximum range can be extended through the use of attachments like the Silencer or Weapon Lasersight to increase accuracy. The Custom SMG is the least expensive submachine gun, and fires the quickest out of every weapon in the game. With no movement penalty, like other SMGs, this weapon is most effectively used while on the move.