This mod basically allows the player to add scopes, silencers and grenade launchers to many weapons that normally don't allow the player to do so and you can see the add-ons on those weapons, which usually don't have them. These weapons include, but not limited to:
Just to name a few.
Extract the files in your S.T.A.L.K.E.R. directory which for retail buyers should be located in C:/Program files/THQ/S.T.A.L.K.E.R. -Shadow of Chernobyl/Gamedata/ and for Steam users it should be located in C:Program files/Steam/SteamApps/Common/Stalker shadow of Chernobyl/gamedata