We were most impressed with the RhinoRail, which weighs only 1.25 pounds!
This rail can take any red dot scope or BUIS-type sight; lasers, lights, sling adapter or even extra shell carriers. When you pick it up, it is hefty, and makes your shotgun look even more ominous. The rails are CNC-machined to tight tolerances for repeatability when using sights and other bolt-ons. The RhinoRail retails for $349; the full-length BullDozer $399.
Both rails feature over 36 inches of rail on four surfaces, and are built using the new NATO Stanag 4694 specification (100% backward compatible with MilSpec/Picatinny 1913 Standards).
ETA claims the rail serves as a heat shield with dissipating fins covering the entire length of the barrel. Assembly is simple, and everything is included – there is no drilling, tapping or other gunsmithing involved. If you're smart enough to shoot a shotgun, you'll be able to install this rail.
Also check out ETA's replacement Tactical Charging Handle and a much-improved and very affordable Tactical Safety replacement for Mossberg 500, 590, 930 and 935s, machined from aircraft aluminum.