Not made to mount on mp5s. - Matrix Real Steel Series Red & Green Dot Scope for HK MP5 G3 Series Rifles

On the top of an MP5 where you mount optics/rails there is what is called a "recoil stop block." This is a non removable ribbed piece of metal made to keep whatever claw mount you put on your MP5 from moving forwards or rearwards. This Matrix Real Steel optic is not compatible with that piece. (Apparently this is also prevalent on many airsoft toys as well from what I was able to find.)