I got this awhile back for my Custom MK36 and I have to say I am very pleased with this red dot sight. Externally the entire red dot sight is made out of metal (with the exception of the lens of course) and for the most part it feels sturdy.
Adjustments require a allen wrench but that is no problem, getting the dot on target was no problem at all. After adjustment the red dot has held it's zero even after rough use.
The mounting brackets (I think that's what they are called, forgive me if I am wrong) are pretty good, will fit onto any Weaver or Picatinny rail . Occasionally they will get loose allowing the sight to slide forward and backwards, something I'm not too happy about but is easily fixed by quickly tightening the screws.
The only other thing which I am not pleased with is how the front lens is held in place. My initial impression upon receiving the sight was that it was either soldered or glued on. As it turns out there are two small screws on the bottom pushing the lenses frame up against the top of the main frame. At one point these screws came loose allowing the lens to literally fall off. Fortunately the lens did not break, and all I had to do was tighten the two screws on the bottom to hold it back in place.
Despite the small lens issue, overall this is a fantastic red dot for the cost. Yes there are nicer ones out there, but for less than $20 you get a very good red dot sight. I plan on ordering more of these for my other airsoft rifles.
Easy to adjust
Easy to mount on a rifle
Dot is clearly visible and holds it's zero
Totally worth the price
Screws holding lens frame in place tend to get loose initially, once tightened the issue does not seem to come back
A little large for some applications (mine is currently mounted on top of a scope)
Rating: [4 of 5 Stars!]