Monstrum Red Dot Mount Compatible with Mossberg 500/535/590/835/Shockwave Series Shotguns

Rmsc plate worked perfectly to mount Osight S onto Mossberg 590.

Perfect fit on a Mossberg 930 and mounting a Burris Fastfire 3.No need for a cheek riser with this.

Value for the money is hard to beat as its less than half the price of its nearest competitor. Machining / finishing also look good. I also like that it uses 3 of the 4 screw holes for a more solid connection and that the center is sunken down to reduce the overall protrusion of the optic (great for top folding stocks with virtually no room on top).The only reason for 4 star instead of 5 is that you have to source your own hardware for pre-97 mossbergs as they use a smaller screw. They do mentioned it buried in the tech details, but I had no idea what year mine even was until I started researching when I realized the supplied screws don't fit. Given the mount already comes with several bags of screws you won't ever use (for various optics other than the one you're using), I'd rather they bump the price up a buck or two and just include the screws for the pre-97 models to save people the time of having to hunt down some on their own to make this work (and ultimately paying much more than the OEM would as they can buy in bulk).

String mount. Great fit. Easy to install. Great value

Ordered the model that claims it fits the Vortex Venom. First of all, the screws included for that red dot are too short and too small of a diameter to use. Second, the mount has 4 posts to align the red dot, but the Vortex Venom only has two indents for posts, and they are not in the same location. It seems the only way to make this work will be to shave off all 4 posts, and drill and re-tap the holes to accept the hardware. Lastly, the provided mounting screws are extremely soft and not quite the right size for the included Allen wrench. Immediately stripped out one of the screws. Do yourself a favor and spend the extra money on a higher quality mount.

Used to mount a swamp fox/rmr footprint on a mossberg 500 and went right on. Well machined and easy fit.

I have a vortex viper and the fit was perfect. The kit comes with several different screw sizes to fit different shotguns. I have a Mossberg 835 and the screws worked perfect. The dot mounted to the adapter with no issues. Good product

First off the mount itself is finished well IMO although like others stated it could have been designed a little differently to reverse it if desired which would solve my particular issues. My 590 is a 1993 (confirmed by Mossberg) with factory installed 8-40 receiver "dummy screws" although they only drilled for three of them and apparently about 1/4" more rearward than most. That puts this mount's rearmost screw boss on the slope of the receiver resulting in a tilt. No idea why my gun was drilled like this and neither did Mossberg when I asked.After drilling and tapping a 4th forwardmost hole the mount fits but there's that taper to deal with at the rear. The Venom sits in the center of the plate but the pins aren't centered, the RDS will reverse on the plate, so the mount reversed solves the tilt issue and brings the optic back a bit (preferred), but will require new RDS mounting holes drilled, and the plate is shaped to fit the Venom so with it reversed it looks a little goofy. Option #1.Option #2, either shim the rearmost screw boss, or cut it off and run the mount with 2 screws only. Not preferred but would work.As others noted the provided screws are junk. The provided "Venom" screws are too small diameter to properly fit the RDS, pic shown. The mount to receiver screws are supposed to be 8-40 but are sloppy fit, sloppy hex, and too few threads exposed when placed into mount. I sourced Hillman 8-40 x 1/4" optic ring screws from local farm supply, MUCH better solution.Cosmetically as others noted it is bulky, I'll taper the ends a bit with a grinding tool probably and smooth the appearance.A lot more than some would deal with I'm sure but I like fine tuning stuff. But those supplied screws need to go. And to answer my own unanswered question from here and Monstrum, the plate is 2.07" in case somebody wants a longer Docter pattern RDS.