The Strike Industries G4 Mass Driver Barrel Compensator should work with the Shadow Systems MR920 Combat. However, Strike Industries states that fitment cannot be guaranteed on aftermarket or non factory Glock slides and frames. I recommend contacting the manufacturer to confirm compatibility.
I bought the G17 model and tried it on my Shadow Systems DR920. It did NOT work. I was able to assemble everything correctly and put the slide back on my pistol, but when I went to pull the slide back it only moved a couple millimeters.