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Questions & Answers
Dose it have a t1 mount? Expert Answer

Yes, the Primary Arms SLx MD-21 1x Micro Reflex Red Dot Sight uses the Aimpoint T1/T2 footprint.

by Ethan, Gear Expert, August 4, 2025
Customer Reviews
Helpful Negative Review
Don't waste your time. by Todd, Verified Owner, September 16, 2025
I had high hopes for this optic, but the "you tubers" were right about the emitter being a problem and causing a massive halo effect if you turn up the dot… and not even all the way. I clicked it 3 times and got this massive red bloom inside the opti...
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2/4 found this helpful
Most Recent Reviews
useless reticle by Ryan Campbell, Verified Owner, September 28, 2025
I should've got the single dot model. I liked the idea of a bdc red dot but the bdc and horseshoe reticles flood the tube with red light rendering the optice completely useless. The chevron is so small ot might as well just be a dot. And the bdc dots...
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2/7 found this helpful
Most Recent Reviews
Great optic by mk, Verified Owner, February 11, 2026
Picked this up recently and I’m impressed. The glass is clear, and the push-button controls are much more tactile and easier to use than a dial. It holds zero perfectly after several hundred rounds. For the price point, the build quality is hard to b...
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Most Recent Reviews
Great optic with good price! by Dan Abling, Verified Owner, June 6, 2025
Lifetime warranty and excellent product!! Highly recommend!!
Read All 4 Reviews
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Product Info for Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive

The SLx MD-21 is an advanced micro dot sight that incorporates the latest technologies and materials to deliver exceptional CQB performance. Weighing only 5 ounces, the SLx MD-21 is both lightweight and rugged, featuring upgraded mounting hardware for guaranteed rigidity and precision when you need it most. If you are looking for a taller mount, check out the SLx 2.26in Mount for use with night vision or if you prefer a more headsup shooting position. The upgraded LED emitter offers complete night vision compatibility as well as a true Red Dot Bright reticle with an ultra-long runtime for full operability in any environment. Additionally, the Autolive technology shuts off the reticle when no motion is detected for two minutes and immediately turns on as soon as you pick it up.image

This Primary Arms red dot sight is part of the SLx optics line. SLx optics have built a reputation for innovation, reliability, and value. All SLx optics undergo rigorous field-testing during development to best serve you in any environment.

Specifications for Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive:

Manufacturer: Primary Arms
Color: Black
Magnification: 1 x
Objective Lens Diameter: 21 mm
Illumination Type: LED
Illumination Color: Red
Adjustment Click Value: 1/2 MOA
Emitter Type: Enclosed
Battery Type: Lithium Metal, CR2032
Weight: 5 oz
Red Dot Sights-Footprint: Not Applicable

Features of Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive

  • Autolive technology extends battery life
  • Fully multicoated lens
  • Top mounted push button controls
  • Night vision compatibility
  • Shockproof and waterproof aluminum construction
  • Standard microdot footprint

Package Contents:

  • Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive
  • Low mount and Absolute Cowitness mount with spacer (1.41in or 1.535in Height)

Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive Orderable Models

List of Orderable Models

  • Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive & 2 MOA Red Dot Reticle, Black, 810027 , MPN: 810027 , UPC: 818500018254 , Code: 29R-RD-CSP6-810027
  • Primary Arms SLx MD-21 Push Button 1x21mm Micro Reflex Red Dot Sight w/AutoLive & ACSS-CQB Red Dot Reticle, Black, 810028 , MPN: 810028 , UPC: 818500018261 , Code: 29R-RD-CSP6-810028
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