Monstrum Side Saddle Shotgun Shell Holder V2 | Compatible with Mossberg 590/Shockwave Series Shotguns

Fits well with the Mossberg Maverick 88 security. Make sure you check the chart. It does not fit some Mossberg shotguns before installing. Put loctite on the shell holder screws. They will come loose over time. If you don't also, make sure you read the directions. Add loctite to the nut on the shell holder side but do not add loctite to the screws with the through bar. Overall, I am very happy with the purchase

Fit right onto a maverick 88, only issue I had was the screw that you have to mount inside the the chamber don’t forget to use blue lock tight ***IMO*** flip the shell holder for best results before mounting, the angle cut helps with getting round out the holder faster for quicker reloads good price & looks good.

Fits good and easy to install

MAVERICK 88: DO NOT BUY!!! The side saddle itself seems really well constructed, it is an extremely tight fit. The problem though as others have said is the screws are GARBAGE. None of them line up as they should, don’t fit properly and when you try to get them installed as per the woeful instructions, and I watched a few youtube videos for clarity, nothing worked. Brought it to someone knowledgeable of firearms he looked at it and barely touched it and said, “nope, return it”. Will be brining it to UPS store tomorrow. YOU HAVE BEEN WARNED.

Screws are of unbelievably bad quality. Crosspin screws stripped immediately when using the hex wrench that came with them. I cannot get them off to even begin installation. Screw that goes into the side of the receiver through the ejector spring barely survived the first installation and is badly chewed up. No way it survives multiple removals for cleaning. Product looks nice and fairly solid, but that is irrelevant if the screws holding it together are of horrible quality. UPDATE: Within 48 hours of posting the review above, I was contacted by the seller and shipped a new product free of charge. The new product worked perfectly. 1 out of 10 for Quality Control 10 out of 10 for Customer Service

EDIT: 2025-11-11 Contacted support on the weekend the item was delivered. Support responded first thing Monday morning, asked for my order # and shipping address. Received a new parts kit on Saturday. Spectacular support!! A note about the extractor screw. On install they will get a fair amount of resistance after about 2-3 turns. This is expected so that the screw is less likely to back out with use (keep in mind this mounting screw also as a nut for the same purpose). This can feel a bit like the screw isn’t correct or is cross threading. Attempted to mount on a Maverick 88 Security. The trigger pin works as intended. However, the screws provided to secure the saddle and replace the extractor screw are the wrong thread. Without the correct screw the unit is unusable. Must be very thin flush head to allow the bolt to pass over the head. Heard other reviews of soft poor quality screws but wasn’t expecting completely wrong thread pitch Contacted support will edit review based on their response.

Rail fits perfectly onto the Mossberg Maverick 88, just be careful not to overtighten any screws when you secure it to the firearm. This picatinny rail gives you so many more options for modern day optics to be mounted for use, although you can use the original bead iron sights through the center channel after install if you really want. Be careful when sliding on the mount to avoid any of the scracthing issues people have talked about, just go slow and thoughtful, I installed mine with no issues. Very impressed by the overall construction and feel, as well as the shells holding snugly without any visible migration.

Fit perfect. Easy installation.

Not sure what all these negative reviews regarding the Maverick 88 are all about. It fits perfectly & only took me 10 minutes to install. I generously oiled the inside of the saddle, as well as the receiver of my gun and it did not leave a single scratch on my gun. Fits like a glove, all of bolt holes lined up perfectly. I used blue locktite on all of the threads just to be sure nothing comes loose which I highly recommend doing. No bolts were stripped, no scratches on my gun, perfect fit for the Maverick 88 as of August 2026. I assume all of the bad reviews are for the V1 of this saddle, where as this is now the V2 saddle and seems much improved. Worth every penny!! Holds shells super snug. Took it to the range today & 0 issues after roughly 75 rounds of #7.5/00buck/slugs. Highly recommend for the Maverick 88!!

This side saddle is well-made and fits my 590 Shockwave shotgun perfectly. To install it, apply some gun oil to the bottom of the saddle to ensure it slides smoothly onto the shotgun. Using oil will prevent scratches. The main screw is a bit tight and requires being pushed from the inside out through the back of the shotgun to secure it, as the hole is not fully threaded for such a screw. Otherwise, there are no major installation issues. In terms of improvements, I would like the hardware to be flush, without a nut on the back to secure the screw.

This fit so nicely on my shotgun. Just a heads up for those who like to clean their guns out: this will add an extra step, but to me it's worth it. Makes the gun look bad ass, plus I added a red dot

High quality but it is not compatible with 590m. Need another drill for the screw

Great quality product! Instructions are pretty bad but simple enough to figure out without them. Comes with additional hardware that’s not needed? As per other reviews a little bit of oil on the product and receiver will have it slide on with minimal scratching. Overall would definitely recommend, looks great and functional.