I purchased this mount for my older model Mossberg 500. Out of the box it is impressive. Much larger than the pictures make it seem.
It's a solid piece of extruded aluminum with 2 attached aluminum side rails, all coated with a very sturdy attractive hardcoat of black.
It installs in less than 5 minutes with just a basic variety of tools. (Center punch or small phillips screwdriver, rubber or brass mallet, and medium flathead screwdriver).
It attaches to the receiver and to the barrel, with an optional third mounting screw to use if you use heavy optics that need more support. I'd hate to see the kind of optics that would require that level of support though! It's plenty sturdy with just the 2 mount points.
The 2 side rails come mounted at the very front of the rail at almost a 90 degree angle. These are held on with a pair of nuts/bolts. Yes, they can be repositioned back up to a couple inches if you desire.
The only downside is that to remove the barrel for cleaning, you have to remove the front mounting. Not a problem for me, since I dont remove my barrel for everyday cleaning.
As far as looks, I think it makes a shotgun look very menacing. Yes, it is more mount than you'll ever need, but the looks and flexibility make up for it.
In summary, a very cool and relatively inexpensive way to make your shotgun the tactical beast you've always wanted. It will sturdily hold any accessory you can think of that can be rail mounted. Highly recommended!