Some of the models like the mk12 and its sight should be subscribed together in order to work well, and the animation pack can only matched with initial model or the models which are marked in that page. Sights and sights in the collection are the addons I current use and I fully recommand you try it since the normal sights are sh*t. And this-FIREFIELD MG "Kemper XL" Machine Gun Reflex Sight [red dot mark] for COBRA [clean glass]-is fantastic. And I have to tell you that some of these can cause conflict and may get a crash( not me I'm fine yet), like the AK74U models in the collection, so make sure you choose the right one you surely want.