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Primary Arms’ (PA) new 21mm red dot sights are designed to combine cutting-edge technology and rugged durability for CQB and close-engagement scenarios.
To start, PA’s SLx line is built for a combination of innovation, reliability, and value. All SLx optics undergo rigorous field-testing during development.
The newest addition, SLx MD-21, is an advanced microdot sight designed to deliver exceptional CQB performance. The MD-21 is engineered to be both lightweight and rugged, and it features upgraded mounting hardware for guaranteed rigidity and precision when you need it.

If you require a taller mount, Primary Arms’ SLx 2.26” Mount is ideal for a head-up shooting posture or for use in tandem with night vision goggles. The SLx MD-21’s upgraded LED emitter offers NV compatibility as well as a Red Dot Bright reticle with an ultra-long runtime. No fewer than 12 brightness settings are available.
The SLx MD-21’s integrated Autolive technology is included to extend battery life by shutting off the reticle when no motion is detected after two minutes, then immediately turns back on as soon as you pick it up. Power is supplied by a standard CR2032 lithium battery.
Two models offer two reticles: a 2 MOA standard dot, and Primary Arms’ ACSS CQB.
Next up is PA’s GLx series, the mid-tier lineup that aims to bring premium technology and materials into a more approachable price range.
The new GLx MD-21s features an advanced Solar Failsafe system that supplements the standard CR2032 lithium battery to ensure the optic offers users maximum runtime.

Like the SLx offering, the GLx MD-21s also features Autolive technology that turns the reticle off after two minutes of inactivity, and switches it back on instantly when motion is detected.
The GLx MD-21s also features fully upgraded multi-coated lenses, an ultra-bright emitter, intuitive push-button controls, and a heavy-duty mounting system, as well as the Red Dot Bright reticle. It is also compatible with the SLx 2.26” Mount for a more head-up shooting orientation or for use with night vision devices.
As with the SLx MD-21, two GLx MD-21s models offer two reticles: a 2 MOA standard dot, and Primary Arms’ ACSS CQB.

Both the SLx and GLx series red dots feature hardcoat-anodized aluminum housing construction. Mount compatibility includes Aimpoint Micro and standard microdot systems. Each weighs just 5 ounces and Primary Arms covers each with a lifetime warranty.
Primary Arms
SLx MD-21 Microdot
MSRP: From $160
GLx MD-21s Microdot
MSRP: From $200
URL: primaryarms.com
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© 2026 UN12 Magazine
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