The Primary Arms GLx MD-21S is a duty-grade 21mm red dot sight with a Solar Failsafe panel backing up the battery and AutoLive motion sensing that wakes the dot the instant the rifle moves.
The crisp 2 MOA red dot runs from a CR2032 with side-mounted push-button controls and night-vision-compatible settings, in a shockproof, waterproof aluminium housing. Low-profile and absolute co-witness mounts ship in the box.
How It Compares
Prefer a ring-and-dot reticle? The MD-21S ACSS-CQB. Tighter budget, no solar? The SLx MD-21. Browse all rifle dot sights and red dots; see our dot size chart.
Key Features
- 2 MOA red dot, night-vision compatible
- Solar Failsafe + AutoLive motion sensing
- Side push-button brightness controls
- Low + absolute co-witness mounts included
- Waterproof, shockproof aluminium; lifetime warranty
Technical Specifications
| Reticle |
2 MOA red dot |
| Power |
CR2032 + Solar Failsafe; AutoLive |
| Size |
21mm micro |
| Mounts |
Low + absolute co-witness (included) |
| SKU / MPN / UPC |
PA-GLX-MD-21S / 810025 / 818500018278 |
What's Included
- GLx MD-21S sight, low mount, co-witness riser + spacer, CR2032, tools, manual
UK Delivery & Support
UK-stocked and dispatched tracked from our UK warehouse — no import duties or customs delays — backed by UK-based support and Primary Arms' lifetime warranty.
Frequently Asked Questions
What does AutoLive do?
Motion sensing shuts the dot down when idle and wakes it instantly on movement — maximum battery life with zero buttons to press.
GLx vs SLx MD-21?
The GLx MD-21S adds the Solar Failsafe panel and upgraded spec over the value SLx MD-21.
