The 
ACM 551
 is a compact, full-metal airsoft optic designed for rapid target acquisition. It features a dual-colour holographic reticle (red and green) with adjustable brightness levels and is typically sold in a tan finish within a "Color Box
 
Key Specifications
Reticle: 65 MOA ring with a 1 MOA centre dot; features 10 levels of brightness for both red and green illumination.
Construction: Full metal body with a plastic battery compartment for durability and weight reduction.
Mounting: Compatible with standard 20mm Weaver or Picatinny rails; some models include a quick-release rail clamp.
Battery Management: Often includes an integrated two-hour auto shut-off function to preserve battery life.
Adjustments: Fully adjustable for windage and elevation (zeroing).