No filibuster here... - Magpul Industries MBUS Front Flip-Up Back Up Sight Gen 2

So what I say about this isn't going to be anything new. I'm honestly not expecting to add anything or reveal some weird perspective that hasn't been thought of before about this or the rear MBUS. So why am I writing? Well, boredom mostly.
Anyone looking to build their first AR, "Pistol" or whatever will likely be told to have backup sights on their rails.
And why shouldn't they? It's a good practice to have them in case your optics take a dump or they don't want to shell out the extra cash. Or maybe they just want to get better with irons. Whatever the reason, shooters want backup sights and these are often where they turn to.
And why shouldn't they? As these are made of polymer, they're very light, but they're also well-made so they're also very sturdy and as a result, they hold their zero very well. These are also pretty cheap, and not to drop names here but I have found Optics Planet to be the best place to get them. A lot of places sell these for around $40-50 with the set going for upwards of $80-90. I've found them on here for as little as $60.
Some folks are concerned these would melt if mounted close to the gas block or something. While not unwarranted, I haven't had any issues with that happening. I've had one mounted almost on top of a gas block, a Superlative Arms adjustable piston block, and if anything slightly in front of it. The way the SA blocks are designed, they vent off excess gases, and carbon and heat as a result. I haven't put a thermometer and run tests on it or anything but aside from some minor carbon buildup, or more like dusting, I haven't had any problems resembling melting or disfiguring on it. So considering I've had it mounted effectively in the blast zone, I'd say you're pretty safe. But it's also got a handguard between it and the gas block. Now if it were mounted on one of those gas blocks that have a rail right on it, then I'd be a little more concerned. Otherwise, as long as you have it mounted on a handguard not directly on the gas block, I think you'll be okay.
As for adjustments and zeroes. These come with their own adjustment tool from Magpul, and as I've adjusted more than one set of MBUS's, I can say that sometimes they move with a satisfying click, other times you have to keep an eye on it lest you leave it halfway between clicks. The inconsistency is a little annoying but as long as you're paying attention to what you're doing, it's whatever. I mean it's a standard front sight post and behaves like one in that respect. Also the tool doesn't work on standard AR front sight posts, too wide.

Now I will say I've found a couple issues with these. I feel they're a bit minor but do need to be addressed.
You need to be a little careful with popping them up. If your handguard is narrow enough, like say a BCM, you can reach around and grasp the two notches on either side to unlock it so the sight springs up. Another way you can do it is to press down on top of it, at least that's what I think the textured depression on top is for. As satisfying as it is to watch and hear it snap up, it can come with a little bite if you use the second method. I've had pinches and blood blisters on my thumb more than once because of it. Even wearing gloves, you'll likely get the material caught and torn up.
Another issue is that these do take up a bit more real-estate as compared to other irons out there. I think it's a bit of a tradeoff with the polymer construction, as I think any less material would risk its sturdiness. It borders a little on clunky, but personally I don't think it takes away from it aesthetically, certainly not in terms of function.

Overall, these are a pretty good option for backup irons/polymers. They're cheap, functional, lightweight and sturdy. They're not likely to snap off and the edges are as rounded as a sightpost can be to mitigate snagging. I mean it's more likely to snag than say a standard M4/M16 style front sight post so there's that. For the few that don't have a picatinny rail to mount these on, sucks to suck, but then I think in a situation like that, what kind of equipment is it that it needs backup sights and doesn't have rails on it?
Iron sights, at least I think, tend to get overshadowed by optics. Yes, it's cool that the age we live in has all manner of optics. Red dots, holographic sights, variables, magnified, scopes, etc. So often when people get their first rifle or their first build, they neglect iron sights, whether they don't train on them or don't bother to even mount them. I personally think it's a good practice to have them. Drilling with irons helps you develop a more consistent sight picture, which in turn makes you a better shooter. I mean, ACOGs aren't indestructible, and maybe you've forgotten you passed the 5-year mark to change out the batteries on your AimPoint. Whatever the case is, it's good to have irons, and Magpul's MBUS are a good place to start.

Also, they come in a variety of colors.