Think you know all there is about the Magpul MBUS? Did you know the MBUS was originally designed for the KRISS Vector?
The early prototype KRISS Vector, like the one seen on Future Weapons, were kitted out with HK MP7 style iron sights. The MP7 sights are a dual sighting system. They flip up for rifle sights. When folded, there are pistol iron sights so you can aim and shoot the MP7 as a pistol.
KRISS wanted something like that. And in the early production KRISS Vector models circa 2008, they came with the Magpul MBUS 2.5. Why are they called MBUS 2.5? Cause that is what it says on the bottom of them.
The MBUS 2.5 were machined aluminum BUIS. They have pistol sights built in when they are folded down.