"Advanced Combined Sighting System" combining Bullet Drop Compensation, Range Estimation, Wind and Leads in one easy to use system.
What a great scope; it's a STEAL at its listed price.
Clear optics, sharp reticle, huge range of illumination, and built-in rangefinder.
1-6x zoom without annoying "fish eye" and true (at least, it looks like "true") 1x.
Excellent fit and finish.
Melonite-like finish, smooth, rounded lines, excellent zoom mechanics, great feel/feedback from illumination and W/E knobs. Matched it to PA's Deluxe Mount: works great on SIG556xi.
P.S. Ordered within 60 seconds of receiving the "back in stock" e-mail notification. Looks like sold out in or about 24 Hrs again? Lucky me!