The MW2 Slimline Pro is probably one of the best attachments in the game, reminiscent of the impossibly clear red dot sight you could equip in previous CoD games.
So, how do you go about attaching this optic to your Gunsmith. There used to be an issue with this optic that stopped played from being able to attach it using the Gunsmith system, but that bug was squashed weeks after MW2 launched.
How to unlock the Slimline Pro optic
The Slimline Pro optic is available as part of the Lachmann & Meer weapon platform. Simply level the Lachman-556 to level 12.
While you're modding your guns, check out our guides to the best Modern Warfare 2 loadouts. Just imagine how good they would be with a clean optic like the Slimline Pro.