Collimator device Primary Arms SLx MD-21 21 mm Micro Dot AutoLive 2 MOA Red Dot

Primary Arms SLx MD-21 is a micro-red-dot designed for users who demand uncompromising precision, durability, and intuitive operation.

Primary Arms SLx MD-21 21 mm Micro Dot – features

• 2 MOA aiming dot — enables fast target acquisition while maintaining accuracy at medium ranges. The ultra-bright dot remains highly visible even in direct sunlight.
• AutoLive® technology — an auto-standby system that extends CR2032 battery life by turning the illumination off when no motion is detected and instantly reactivating when movement resumes.
• Night vision compatible — the unit includes NV-compatible settings for safe and effective night operations.
• Top controls — adjustment buttons are placed on the top of the housing for intuitive access and to avoid interference in tandem mounting configurations.
• Multi-coated lens — provides high light transmission and minimizes reflections for a crisp, high-contrast, distortion-free image.
• Anodized aircraft-grade aluminum housing — matte black finish offers shock resistance, corrosion protection, and rugged field durability.
• Waterproof and shock-resistant — meets IP67 environmental requirements for reliable operation during rain and in dusty environments.
• Two mounts included — absolute co-witness and lower 1/3 co-witness allow optimal height selection for various firearm setups.
• Micro Dot footprint — fully compatible with popular micro-red-dot mounts from other manufacturers (e.g., Aimpoint Micro).

AutoLive® and the 2 MOA dot

The SLx MD-21 includes AutoLive®, which automatically places the sight into standby when no motion is sensed and instantly reactivates when it is used again. This maximizes energy savings without manual power switching — ideal for dynamic tactical, sporting, or hunting scenarios.

The sight features a 2 MOA dot that combines rapid target acquisition with the precision needed at extended ranges. The ultra-bright dot performs reliably in full sun and low-visibility conditions alike. NV compatibility further extends its utility for nighttime operations.

Durable and functional

The SLx MD-21 is built to withstand harsh conditions. Its rugged aluminum housing with anodized finish, IP67 rating and shock resistance ensure dependable performance in demanding environments. Nitrogen filling prevents lens fogging.

Compact yet versatile

With a standard Micro Dot footprint, the sight is easy to mount on most platforms — from ARs and PCCs to carbines, shotguns and pistols. The package includes two mounts — absolute co-witness and 1/3 co-witness for full customization relative to mechanical sights.

Top-mounted controls allow quick operation without interfering with other accessories or side mounts. The multi-coated anti-reflective lens provides a clean, contrasty view with minimal glare, significantly improving accuracy and shooting comfort.