I have this mounted on my AR-15 with a Monstrum low profile Picatinny riser mount. But since the Rona hit, I haven't sighted it, so I can't account for its accuracy yet. I'll update the review after I have a few hundred rounds in.UPDATE – 1/9/19I changed my 1-star to 5-star review because the problem describe in my initial review isn’t with the sight, but rather the user instructions supplied with it. Also the company’s excellent customer service rated an upgrade - I was supplied with a new unit even though the warranty had expired. My original review was based on me trying to insert the CR2032 battery called for in the instructions. The unit actually takes the smaller CR1632 battery – that is what caused the problem. I removed the old battery and disposed of it when I needed a new battery and a couple of weeks later I checked the manual for what I needed to purchase to replace it. The ORIGINAL POST and UPDATE are below. One IMPORTANT note: the company still has the wrong battery size in the instructions. I have been very satisfied with this red dot’s performance on my AR-15; it holds zero and has a clear image with the perfect size red dot for me. This is an entry level sight, but for the money it can't be beat. If you want to try a red dot and don't want to spend big bucks without knowing if it is a type of sight for you, this is an excellent choice.ORIGINAL POSTI just tried to change the battery in this sight for the first time and I could NOT get the new battery in! All of my other red dots have a ridge/lip that holds the battery in place when you screw the cap on the battery compartment. This unit does not have one and it is impossible to get the battery to stay centered as you try to screw the cap on under pressure with the fine threads that it has. I tried to contact the seller at the email address they posted to respond to in another person's post and my email server says it isn't a valid email address. I would WARN anyone that considers this unit that after the first battery dies, you will NOT be able to replace it and the seller poster a false email address to respond to. The sad thing is that I loved this sight on my AR and had intended to use it regularly. Be forewarned!UPDATE 1/4/19The email address mentioned above was actually good if I inserted the missing "@" where it was omitted by the SELLER. I just copied and pasted it without paying attention to the SELLER's error. I corrected the address and I DID get a response that said they would supply me with a new unit after I supplied them with my order number. They even extended the warranty to cover my sight. I look forward to the new sight because I would like to put it back on my AR. I might be dealing with them directly in China for all I know and the exchange might take some time, but I guess time will tell.I picked this up thinking it would be a great, cheap addition to an air rifle. Installation was easy, I boresighted to “close enough” and immediately had problems zeroing. Red dot sights are supposed to be “parallax-free.” (Technically speaking, they’re not; they’re really stinking close, though.) Parallax is caused by any number of factors, but is noticeable in the way that your point of impact shifts if your face isn’t lined up consistently (and centered) behind the sighting device. Look in the picture I attached to this review. Notice how with the OTW sight the red dot shifts slightly against the garage door as the perspective is moved from side to side. Even small shifts can change your impact by inches. This is a huge problem if you’re shooting small targets or controlling pests/varmints. This shift is the parallax that the OTW sight’s own documentation says it shouldn’t have. (Again, see attached image.) Compare that to the TRS-25 in the lower images. The dot doesn’t move at all, despite having the same wild shift from side to side. This is how red dots are *supposed* to work. (I apologize for the crappy quality photos. Early morning sun in the eyes played havoc with my phone.) For reference, that garage door is about 30’ away. Technically, the TRS-25 should have about 1/3rd of an inch of parallax at that super short distance with such a huge side-to-side swing. (Parallax increases as the target is closer to the sight.) The OTW, on the other hand, has almost 2 feet of parallax!Red dot sights shouldn’t have parallax because the tiny laser inside reflects off of a parabolic lens on the inside of the sight. This parabolic lens makes sure that the light from the laser is always on the object that the muzzle is pointing at, even when your eyes are off-center. The problem is that the OTW sight doesn’t have a parabolic lens. It has a flat lens, which causes it to have tons of parallax. This isn’t a manufacturing error, this is a blatant design flaw that was no accident. The documentation claims that the OTW should be parallax-free, but clearly never had the proper lens installed.I’ll admit: the red and green dots are both decent on this one. And the construction seems solid. The glass isn’t great, but when you aren’t looking through it with a camera with the sun shining into the first lens the image is fine. The problem is that the sight isn’t actually what it claims to be! DO NOT BUY this red dot. My recommendation is the TRS-25, instead. It’s commonly used in competitions and yet is easily found for $70-$100. Yes, that’s a lot more than this sight, but this one isn’t what it claims to be in the first place.After some adjusting I shot a couple good groups, but then it shifted way up and right and wouldn't adjust. Returned.Used on my MCK and seems durable. Like the compact size and low weight. Dot isnice and bright on 5 setting, good budget red/green dot.I will start with, I own many guns and many optics. My daughter gave me a $40 Amazon gift card and i needed a red dot scope for a Ruger 10/22 Charger. I thought about saving the card until i had more money to add to it and buy a higher priced name brand. Then i found this guy on Youtube called 704 Tactical. He did a review on this particular optic. He beat the crap out of this thing and it took the abuse. For under $40 i am really glad i bought it. It comes on a pretty solid mount, mounts easy of course, brightness settings are good, looks really good on a Ruger Charger pistol with AR15 pistol/paddle brace attachments. Its great for rimfire recoil and i will purchase another one to put on a 9mm sub gun. I am confident it will take the recoil.I bought this for occasional use on 22 rifles, pistols, or crossbows. It appears to be just about perfect for that use. It is actually small enough to use on a handgun, although it would be nice if it had several different reticles. Can't get everything for less than 30 bucks though. I can't rate it higher for accuracy only because I haven't taken the time to fine tune it yet. But it appears to be one of the most versatile dot sights I have so far.