CoSight Optic Adapter w/ Integrated Backup Sight Mounts

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  • $99.00
  • Regular price $159.99
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CoSight is a low-profile RMR-cut optics adapter for Mossberg shotguns with drilled and tapped receivers.  What makes CoSight unique is that it integrates G17-type Glock-compatible handgun sight mounts into a 1-piece adapter system to provide Back Up Iron Sight (BUIS) and co-witnessing capabilities.

Weighing only 2.5 oz, the Cosight adapter is machined from solid 304 billet stainless steel and is finished in an Armor Black Cerakote coating.  Weight reduction pockets have been machined into the underside of the adapter to achieve its light weight, while the stainless steel body provides maximum strength around the optic mounting threads and rear dovetail mount.

Utilizing the array of G17-type Glock-compatible handgun sights on the market, users can choose various sight types from plain black to white-dot to tritium night sights.  Users can also select the height of their sights for different co-witnessing schemes.  CoSight has been designed so that standard height Glock-compatible sights co-witness lower 1/4 with most optics, providing the largest clear field of view possible.  However the user can choose lower 1/3 or absolute co-witnessing by choosing an appropriate, taller (suppressor height) sight.

Co-Sight's mounting design ensures the only contacts points with your firearm are along the machined, grooved area on top of the receiver, which locks the adapter into place.  Even though it is contoured to follow the profile of the receiver, CoSight does not contact the face of the receiver and will not mar your firearm's finish like designs that contact the face when mounted.

Fits the following Mossberg drilled and tapped shotguns - 500, 505, 510, 590, 590A1, 535, 835, 930, 935, 940.

Like all our products, CoSight comes with the Defender Tactical Lifetime Warranty. 


Customer Reviews

Based on 4 reviews
Tim Smith

This Cosight is at once very practical and very well machined. It sits nice and tight on top of the 590's receiver with no gaps or protrusions. The finish is super even and the machining is excellent. I had a little trouble starting the rear sight of a Trijicon GL01 Bright and Tough set. I don't have a whole lot of experience with these things but I thought that maybe it was too tight to safely continue. I called Defender Tactical to ask their opinion. Wes offered to install the sight in their shop, which he did, at no charge. Can't beat that.

Tad D.
Best Optic Mount Ever!

Quality, precise fit and finish and it works well. Thank you so much for all the products an services for this community.

Shon Workman
The best solution for a dot sight

This mount is a game changer and even though I opted not to get Glock sights it’s nice to know that I can get them if I wanted. The installation was very straightforward and easy, the mount holds on very solidly and the Holosun 507C that I chose has held into place on the sight very snug too. Disclaimer for my review, I had to get the magpul low cheek riser kit and use the 1/4” riser for my cheek weld, mileage may very but if you’ve got a pretty low profile cheek weld, consider getting that kit just in case. As for the shooting portion I’ve run it through 30 full power slugs, buckshot, turkey loads, and birdshot all pretty back to back and I don’t feel any looseness from the best or dot in any way. This product is definitely a 11/10 purchase for me as it has solved a big aiming crisis I had for switching loads and barrels

Awesome product

These rails are just awesome. Now able to really aim the Mossberg including the Shockwave and with a Holosun 507c x really nice set up. I installed night sights front and rear. Great service and great product. Highly recommend.