Primary Arms Classic Series 21mm Micro Reflex Sight - 3 MOA Dot

Manufactured by Primary Arms
MPN: 810035
Manufactured by Primary Arms
45 Reviews

In Stock

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The Classic Series™ proves that entry-level optics don’t have to be poor quality optics. Unlike some other brands, Primary Arms doesn't use the word “value” as a euphemism for “junk”. Classic Series red dots are perfect for the budget conscious and the new shooter. Every product is inspected in their facility in Houston to ensure you are receiving the best quality product as the other three tiers. These red dots are backed by the same excellent customer service and support as all other Primary Arms products.

The Primary Arms MRSC Micro Reflex Sight is a continuation of the new line of red dot sights designed specifically for mounting to pistol slides. The Micro Reflex Sight is optimized for compact and micro compact pistols for concealed carry as it features a slightly smaller 21mm lens to keep the profile as slim as possible when mounting on smaller pistols eliminating any overhang on the slide. Even though the lens is smaller than the mini, the square profile offers an unobstructed field of view allowing you to have a clear sight picture every time you present your pistol. It utilizes the RMSc footprint for a wide range of compatibility with milled slides and adapter plates and houses a bottom mounted CR2032 battery offering up to 40k hours of battery life on the medium setting. With 10 total illumination settings, and a daylight bright 3 MOA red dot, this reflex sight is sure to be quick to pick up and easy to use. The lens is fully multicoated for scratch and fog resistance and the 6061 Aluminum housing is extremely durable. If, you are looking for a new red dot for concealed carry you can't go wrong with the Primary Arms MRSC.

Note: After 12 hours of illumination continuously running, the illumination will turn off. To turn the illumination back on, press one of the brightness adjustment buttons and the reticle will reappear.

  • Fits RMSc footprint
  • Compact 21x15mm lens
  • Optimized for micro-compact pistols
  • 3 MOA Red dot
  • Includes CR2032 battery
  • Up to 40k hour battery life
  • Auto-off turns off illumination after 12 hours
  • 10 Brightness settings
  • Compact and lightweight design
  • Fully multicoated lens
  • Backed by Primary Arms Optics Lifetime Warranty
See More


Battery Life25,001 - 50,000 Hours
Battery TypeCR2032 3V Lithium Coin
BrandPrimary Arms
Brightness10 Settings
FinishHardcoat Anodized
ManufacturerPrimary Arms
MaterialAluminum - 6061-T6
Mount CompatibilityShield RMSc
Optic SeriesClassic
Reticle3 MOA Dot
Reticle ColorRed
Weight.56 oz.
  • Learn More About The Primary Arms Micro Reflex Sight
  • Check Out The Micro Reflex Sight In Action
  • Micro Reflex Sight Review: Beyond Seclusion
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to

Ratings & Reviews

45 reviews


21mm micro reflex sight-3moa dot


High quality product. Fits my Canik TP9 Elite SC perfectly. It comes with a variety of mounting screws, however I did have to buy screws to fit the Canik mounting holes, no big deal. The lens is very clear, and the adjustable dot brightness is nice as you can adjust it to many eye sights. Great optic at a great price point.

Not bright enough for outdoor use

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This optic is a great price but it need to have 2-3 more higher brightness settings. This is great for indoor use, it just needs to be a little brighter for the sun outdoors. Other than that it was easy to install and worked as the instructions read.

Rock solid on the CR920!

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Currently running this on my Shadow Systems CR920, I used the screws Shadow Systems provided and after placing the shim, I had a glove-like fit. The dot is relatively easy to acquire on the draw and plenty bright. The MRSc is a great alternative to the RMR, and a way better price. My only wish is for a shake-awake feature.

No frills keeps the price down and quality up


I had absolutely no failures with this on 2 different firearms so far. I had it on an IWI Masada slim (9s) for about 400 rounds. No problems. The fit (footprint) was just fine. I used the screws IWI includes with the firearm. Then I went and got the Taurus tx22 compact and put this dot on it. For the 22 I used the screws included with the site. Again no problems. Is this site waterproof , is it all kinds of drop proof with fancy features nope. However it doesn't cost $250-600 either. So know all that before you buy it. The only complaint I have is it could use 1 maybe 2 higher brightness settings.

A Decent Value

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Setup, fit, finish, and function are just what I expected and it is a great value. The only thing that concerns me is the need to remove the unit to change the battery and the fact that the bottom is not sealed or has a sealing plate. I will use it for training with the use of optics on .22 caliber converted Glock pistols with the Advantage Arms kits.

Pretty solid little reflex for a CCW

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I like it. You really can’t beat it for the price. Sits nice on top of my Hellcat OSP. Only complaint is that the battery doesn’t last 846,917 years and that you have to remove the optic to change the battery, but that’s overlooked thanks to the price.

Great optic, Great price

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Great price for a great optic. Easy to put on easy to zero and great for 1st optic!!

Great red dot for FN Reflex

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I put this on an optics-ready FN Reflex. Perfect width to match the pistol width. Excellent marks on dot stability, machining tolerance for mount screws, and dot brightness. Note that for the FN Reflex, you need to use the 8mm screws that came with the pistol, not any of the screws that come with this optic.

Wrong screw size

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Haven’t used the red dot yet but while trying to install I had some difficulties trying to find the right screw size for it. I have lots of different red dots and all sorts of screws for installation but nothing seems to be short enough to touch the plunger on right side of red dot,other than that the red dot looks nice but cant use it without proper screws.FYI it looks good on PSA micro dagger

Fits like a glove


Purchased this because I wanted a dot to start with until I can purchase a Holosun down the road And I also didn’t want to deal with the hassle of purchasing a mounting plate. This fit directly to my Glock 48 MOS. It came with everything needed to install minus the thread glue. But the battery is located under the red dot so I chose not to use it anyway. Hopefully this info helps someone else. But all in all happy with my purchase.