I think this is a decent product. It has a small form factor and I was able to get it to fit under my 45 BB gun. It is pretty bright and has a good adjustment range.
The screw on the bottom of the device adjusts the elevation (up and down) and I recommend setting it so it shoots about 1 inch above the laser dot. In other words you want it straight. This way it works at all close-ish ranges before gravity and drag can do its thing and drop the projectile's trajectory.
If you set it exactly on target then it will only be accurate at that exact range which is likely what you do not want.
The hex screw on the left side of the device (closest to the front) adjusts the right/left. Turning it left (counterclockwise) pulls it to the right. On the off chance you put it on and you cant get it adjusted (out of range), you might try hacking it like I did. On one gun I used aluminum foil and put on the lefthand side of the rail to force push it to the right.
There is what looks like another hex screw on that same side towards the back and I have no idea what thats for. It might be a locking screw but I wasnt able to turn it... or I over loosened it and the little threaded piece fell out.
Just to be clear this is a laser pointer. I think their marketing dept is confused, calling it a "red dot". Technically true sort of but confusing as it is not an actual "red dot" optical site. In fact, THEY got confused and have stuff like "crosshair" and anti-reflective optical surfaces which do not exist.
Finally lets be real... if you put this on a real gun, it likely wont work very well. I mean cmon...its cheap. It is NOT shockproof or anti-vibration. If using on a real gun, I highly recommend the loctite approach (and then never take it off the gun), or spend a bit more cash for a true gun site. I'd stick to BB and airsoft and nerf for this.