Bought one of these to slap on my Harrier, and it did not disappoint. Much more accurate than the included scar and an additional BCAR I own, and was able to hit a 2 in wide grouping at 40 feet 90% of the time. Also the aluminum shroud is a godsend and has kept me from breaking the scar after hitting it on walls and railings by accident. Left minor scratches on the aluminum but its better than paying for another scar altogether.
One minor thing I noticed is that the dart trajectory did change when I rotated the placement of the scar (not adjusting, just putting it on a different way), but it can be used to your advantage if you get it adjusted and zeroed properly on your sights.
