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
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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


So good.

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Mounted on a 10mm G40. Nice low profile and holds zero well. 10mm is a punishing round. So far, so good.

"Micro" MEANS micro

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I settled on the 21mm micro mounted on an EGW mount for a S&W M&P 22 Compact because of the gun's narrow slide width and the Micro's very light weight, so as to not interfere with slide recoil causing FTEs. It matches-up perfectly (NO slide overhang), not too tall, and zero function problems with CCI Blazer ammo. I really enjoy the wide range of dot brightness selections. It's a small screen, but that works for me on this gun for my purposes.
VERY reasonably priced especially considering the lifetime warranty.

Great little red dot

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You can't go wrong with the price. Not to mention the lifetime warranty. Glass is very clear. red dot is very accurate. It's perfect on Canik MC9. Highly recommend this product for your micro carry!

Absolutely outstanding optic - for the value or otherwise

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I mounted this optic to my Sig Sauer P365XL and have nothing but great things to say about it! This red dot is spot on, has great adjustable brightness levels, and has held zero after hundreds of rounds and consistent concealed carry use. On that note, the optic is a great size and is very comfortable for a daily concealed carry. The construction is also a nice durable metal instead of polymer like comparable red dot sights.

The only improvements that I could recommend to PA is possibly adding shake awake functionality and/or solar cells to the top.

Not too shabby!

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If the features you only use 2 times a year really matter to you i guess this isn’t for you. But for the people that live in the real world and conceal carry, this is for you!
The window size is awesome for a rmsc. I have a 407k and the window size is better than the 407k. Reviews say its not bright enough but thats nonsense. Plenty bright and with a (not as strong) aluminum, this allows for a bigger window!
I could buy 2 for the price of a holosun. Recommended 4 star only because it is not enclosed.

Nice red dot for the Hellcat RDP

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It does fit the hellcat rdp without a plate. It has the same RMSC footprint as other red dots. Mounts directly to the gun. Make sure to buy the additional screws they sell for it which only costs $8.

Great optic

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I just leave mine on. Didnt take much to get it set at full co-witness. dropped right in just fine. comes with different mounting screws. thank god, because i needed two different lengths due to a pin on the r7 mako. but it works and works great. love me some primary arms!

Nice Optic but...

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Nice optic mounts up great on a hellcat. M4s for the hellcat not included though so either gotta buy or make your own. Not too sure on how well it holds zero though as my hellcat is extremely tough to keep zeroed (me or the firearm not sure). My slide lock also was not locking open all the time either, not sure if it is my mags or the weight of the optic will have to remove and try again. I recommend this product if you have a reliable firearm to install it on

Great optic at a great price


The optic fit right into my hellcat pro. Like other reviews, the screws were about 0.1mm too long. While I could have added a base plate, I added small washers between the head of the screw and the optic. I now have a tight, snug fit with a clear picture.

This is a $150 optic, so it is not expected to have the additional features of a Trijicon or Holosun. You get a SOLID optic (aluminum housing) that you can rack, check, and anything else you would typically do with a RDO and be confident in it's ability to perform (don't cry about the bottom mount battery, 40k hour battery life).

Good alternative to 407 + perfect dagger screws

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I can confirm the supplied m4 optic screws fit the optic perfectly for the dagger micro slide. Actually, a better fit than the PSA supplied long screws. Also holds zero quite well and keeps the pistol well concealed and carries well.