I own this sight. This is my first optic, as I am relatively new to Airsoft. I received it last week, and have used it for target practice since sighting it in. I have not used it in "combat." I offer that background for context purposes.
That said, I think this sight is great for the $. I don't see a significant difference in the brightness settings between 1 & 3, but all are functional. Green dot seems sharper, but red dot does show up better in daylight.
The sight is relatively easy to calibrate, but does require significant adjustments for what I perceive to be insignificant changes in target distance. Example: I needed to adjust the sight when changing from targets located 20-30 ft away to targets 50-60 ft away. This may be the case with ANY sight, and this is where my inexperience may be coming into play. So take that observation for what it's worth. While easy to calibrate, it does require an (included) Allen wrench/key. This isn't that big of a deal to me when shooting target practice, but were I to use it in combat and require an adjustment, it would be a drag.
The unit is relatively easy to install, but the sight will slide back & forth in the mounts with proper force. I suppose if I knocked it hard, or bumped into something while running, the sight might slip out of its bracket mounts. I haven't really muscled it on with a screwdriver, but as it appears to be secured tightly to the gun, I'm not sure how much tighter the grip on the sight could be even if I were to do so.
All in all I am satisfied with this purchase. Had I paid $40 or more, I would have regrets. But for $19, I can live with what I perceive to be its minimal short-comings. Good sight for the money. Seems to be well-made with quality materials. I'm giving it 4 stars because I wish it was darn near immovable once secured on the gun (and it's not), and I wish I didn't have to use an Allen wrench to calibrate it every time. Maybe the next optic I purchase will have thumbwheel adjustment... and will probably cost me more than $19. ;_)
Good entry level sight, and since I'm an entry level Airsofter, we're a good match.
Nice weight; feels like a high-quality piece of equipment
Works as advertised
Sights in well
Easy to adjust with the included Allen wrench
Minimalist look meshes great with my gun (G&G GR300 Long)
Comes with an extra battery
Nice bang for the buck
Will shift in the brackets slightly with significant force applied
Have to use an Allen wrench to adjust the sight
Rating: [4 of 5 Stars!]