Bought this for my Remington 870 Express Tactical. Mounting was very simple and involved removing the two action pins which hold the 870 trigger group in place. The pins are replaced by double ended screws (Chicago screws) that tighten from both directions. These, in combination with a thin rubber adhesive strip allow the mount to fit snugly to the weapon without damaging the finish. They hold on to shells very tightly from either a primer-up or primer-down position. Only difficulty is with the rubber retainer piece. When loading the side saddle, the rubber tends to squish around and twist, making remaining shells a bit tricky to load. If this happens, DO NOT FORCE THE SHELLS IN! This may damage the rubber and deform it considerably. I figured out that if you twist shells while sliding them in, they go in smoothly without binding up the rubber retainer. Knowing that, this thing is good to go! Durable, made of aluminum, and fits well. Definitely would use it on my other shotguns.