The Primary Arms SLx MD-21 puts AutoLive convenience into a value-priced 21mm red dot sight — a crisp 2 MOA red dot that wakes on movement and shuts down when idle, so the battery lasts and the dot is always on when you mount the rifle.
Side push-buttons cycle brightness (night-vision compatible) and the aluminium housing is waterproof and shockproof. Low and absolute co-witness mounts ship in the box.
How It Compares
Want solar backup? Step up to the GLx MD-21S. Prefer a rotary knob? The SLx MD-25 Gen II. Browse rifle dot sights and see best budget red dots.
Key Features
- 2 MOA red dot, night-vision compatible
- AutoLive motion sensing (CR2032)
- 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; AutoLive motion sensing |
| Size |
21mm micro |
| Mounts |
Low + absolute co-witness (included) |
| SKU / MPN / UPC |
PA-SLX-MD-21 / 810027 / 818500018254 |
What's Included
- SLx MD-21 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
MD-21 vs MD-25?
The MD-21 is the smaller 21mm push-button model; the MD-25 is a 25mm tube-style microdot with rotary knob controls.
Will it co-witness with my irons?
Yes — the included riser sets absolute co-witness on an AR-15 flat-top.
