Sightmark SM25016 LoPro Mini Laser Sight 5mW Green Laser 520nM Wavelength (50yds Day/600yds Night Range)

(1) 100% as advertised. ... (2) I've had one mounted for a year now on my test rifle, an M-4 in 5.56. I have put over 6,000 rounds on this laser. I have dropped it from a two story building onto concrete 5 times, frozen it in a block of ice in the freezer for two weeks, left it submerged in water in the pool 12 feet deep for a week, thrown it down range and against a wall several times, baked it in the oven in its operating temp range, left it outside in the elements (sun, temps of 100 + degrees, rain, snow, ice, temps of below zero) and generally abused it. Looks a lot worse for wear, case scratched and dinged. I did cover the laser aperture with a few layers of tape for the throwing and dropping portions of my testing. But after all that, and all the other abuse and use since, it has never failed to work and has not lost its zero. I'm not sure about each one that comes off their production line but the one I got is definitely engineered for greater than its rated published specs. The 'normal' shooter doesn't do this with their gear, I understand, but I really wanted to test it so I did. ... (3) Yes, its a 'block' chunk thing and maybe 'mini' is not exactly suited for the name as its not the smallest thing if you wanted something smaller. The switch, well, that could be better and its not the best thing and the wire could stand to be a few inches longer maybe (hey SightMark, maybe a better and more mainstream compatible switch as an option). ... (4) I've used all sorts of brand name lasers on my rifles. But I wanted something else as none of them seemed to hit the mark in what I was looking for. So I started looking for a rifle laser with long battery life, durability, easy to change battery that used CR123 type batteries for compatibility with my lights so I didn't need to keep different batteries on hand (plus I get my CR123A's for free anyway), and was really tough and did not need me to take out a second mortgage on my house to purchase. I took a chance on this laser because someone else had told me about it and how they had generally abused it and it still worked and held zero. I approached it with skepticism and the worse thing was that I would have wasted $100.00 if it did not work out, but it worked out and its among the best money I ever spent on firearms stuff.