MP5Ks are surprisingly different from their base platform the MP5. So much so that they need their own page to explain the differences. First of all and the most noticeable is that they use version 3 gearboxes, not version 2. This actually gives them a distinct advantage because version 3 gearboxes are typically more reinforced than version 2. Also, they do not use the same hop up unit. That, gives them a disadvantage because there are no known aftermarket hop up units. However, being CQC exclusive guns, an upgraded hop up unit is less needed than most other guns considering you will likely never see its maximum range if you uses it exclusively for CQC. Another difference is the trigger itself, it is extremely long and not compatible with normal MP5 triggers.