So, to begin I have what I describe as 80s hair metal hair. Thin, fine hair with curls in the back and straighter in the front with some moderate frizz, but very soft (only it doesn't look soft). My curls are stringy and not wide groups of hair which looks romantic. Mine looks wild. I also have bleached hair and the first step stripped some toner out of my highlights making my hair look much lighter than when I started
With longer hair, I would rock the curls with some curl cream or gel and go about my simple air-dry life. Once I got a new job, I wanted a sleeker more professional long bob, which doesn't bode well for my texture but my stylist loved cutting off the 10" of hair and it looked great when he straightened it. I asked about keratin while with him and he doesn't do it but offered a reverse perm. I wasn't down for the curl to straight look when my hair grows, I wanted something that would "wear off" over time to my regular texture.
Enter this product. Now it arrived and I tested positive for covid the day after it arrived ... so I have some time on my hands. Once I got through the hell of the first few days I was feeling strong enough to get to my hair. Granted I have a bob and knew it wouldn't take the 4-5 hours some other reviewers mentioned. Before applying it, I lost my sense of smell, but this still burned my eyes like cutting onions - but not too strong.
I loved how it looked after I straightened it with the product in - it was so sleek. I kept it in for about two hours and considered overnight but figured the fumes wouldn't be healthy.
When I was rinsing it and applying the mask, I looked and could tell some of my curl was relaxed but still intact. When blow drying it did not curl under like it did with step 2 in but did the middle age mom upward flip (aka like the "Rachel" in the 90s)... I will still need to flat iron for my desired results.
I guess if you made it this far you are like me and need all the details. To sum it up, it helps and works. It's not going to make your curly hair perfectly straight without some styling help. Maybe over time - the good thing is I have enough for one more application

I applied the treatment on my wig to revive it ,and the outcome was incredible! It have shine to the hair. It does have a very strong scent so don't use if sensitive to smells

EDITED WITH UPDATE, PLUS ADDED PHOTOS:
Jan 11, 2023 - it took over 3 months for the super-flat-&-super-straight texture to settle back to anything resembling my natural curly-wavy hair texture. Let's just say my face is 'fluffy' so the volume from my natural hair texture was more proportionate a style for my face. AFTER 3 OR 4 MONTHS I ended up cutting off nearly all of my hair, th sedimentary had been keratin straightened - not because I hated it, but because I became completely obsessed with the modern mullet!

Re: washing - washing did not significantly alter my hair, it remained very straight and very shiny through many washes over 3 (maybe 4?) MONTHS. Fog was not an issue at all, my hair stayed very straight in all of those situations when it normally would have reverted back to unruly curls (i.e. outdoor fog, or steam while cooking, or sweat from exercise). So I'll say the product and treatment are very long lasting.

The ends did feel a little dry, like the keratin treatment closed off my hair from absorbing any of the deep conditioners I typically apply throughout the month. Beyond that, I don't have complaints about the product or how it changed my hair.
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March 4, 2021 - I've always been a DIY-er, and I have fine, 2b/2c curls, below-shoulder-length hair that tends to be quite frizzy when allowed to do its own thing -- especially when I travel to more-humid parts of the country. I've found if I blow-style my hair straight, with a large round brush, I can go a full week without needing to wash/ re-style -- but there's always the risk that if it's a muggy, foggy, or rainy day, I've got problems. I stumbled across this product, watched several videos & reviews, and decided to give it a go. I followed the directions to a T, and found the application techniques that Eliana Jalali showed in her video (uploaded here to the product) extremely helpful.

The results are that my hair is VERY smooth, and VERY straight... maybe too straight? What I mean by that is before doing this treatment, when I just blow-style straight, it still has plenty of body; whereas right now it's quite flat, but shiny straight. That's why I rated 4/5 stars. As of today, I haven't washed & styled since doing the process 5 days ago, so I'll update my review once I've done a couple washes & see how it fares.

A few notes/ observations:

1) I did this treatment 2 days after coloring, and it definitely lightened the color, probably a full shade or slightly more. My thought process for doing things in that order was that I was concerned that if I did the keratin treatment first, and colored afterwards, the color might not "take" as well. I plan to research this more. But either way, it would be an easy adjustment to color slightly darker than intended, then do the keratin.

2) As mentioned, my hair is slightly-below-shoulder length, but I have a less-than-average amount of hair, and what I have is moderately fine. I will easily get 2 uses out of this first package -- possibly even 3 if I find a good clarifying shampoo (I used a lot prior to applying the keratin). But if you have thick hair, or a lot of hair, or very long hair, you'll probably only get 1 or 2 uses.

3) Do not underestimate the fumes, while they're not horrid, they're definitely fairly irritating. I really needed my wall-mounted/ large mirror in my bathroom to feel like I could see all angles of my head -- utilizing the two adjacent medicine cabinet doors, I can see the back fully, leaving my hands free for the process. But my bathroom is in the center of my house, with no nearby windows, and the fan is only in the shower area. That became a bit of a problem, as my eyes began to water and my nose began to run. I finally pulled out a small fan & set it on the counter, on low to blow away the fumes, but if I continue using this, I'll need to figure out something near a window I can open.

4) I opted not to use gloves this first time around, most (all?) of the videos I watched, the demonstrators didn't. And I'm guessing I'm like a lot of people, when I straight iron my hair, it's a two-handed process... meaning I hold the iron in my right hand, and handle my hair with my left. Which means my left palm & fingers got a thorough coating of the product, AND, in handling my heated hair now & then, the keratin actually bonded to my left palm & fingers, whoops! That took a solid 5 days to wear off, even with washing my hands constantly during this pandemic. It was totally invisible, and really nothing more than an annoying feeling, but I mention it so you can make an informed choice on whether you want to wear the gloves.

I'm a 58 year old black woman who finally got tired of coloring my gray hair since I'd get the "white line of demarcation' within weeks. Then, I'd have to use that brush-in crap, or wear headbands - I said screw it. But in case you've never dealt with gray hair, it is some wiry, tenacious stuff (and the edges - OMG!). So I would continue to get a relaxer (I use Affirm, which doesn't seem to dry it out as much), and that was fine; it would straighten it, but kinda sapped the life out of my hair.
So I'd heard a lot of talk about these keratin treatments doing essentially the same thing as a relaxer, but leaving your hair w/more body, and shine. I read the reviews and since I was due for a touch-up, decided to go for it.
HOT DANG!! SHUT THE FRONT DOOR! It's like elves came in my house last night and replaced my hair with beautiful, soft, shiny fairy hair.
The process is a little tedious (it took about 3 hours), but the payoff is completely worth it. And it's WAYYY cheaper than the $175 my hairdresser charges.
I washed my hair well w/the #1 shampoo, dried it with a wide-toothed detangling comb and my fingers, and sectioned into 6 sections. The kit includes gloves, but I did buy a dye brush to apply the #2 solution, and a very fine-toothed comb to comb it thru (thinking the finer the tooth, the smoother the hair?). I just used a glass bowl to put the solution in. My hair is chin length, so brushing solution on the top of each section by the roots and then down by the ends kinda morphed into just brushing the solution on the whole length, and then I used the tiny-tooth comb to comb it thru. The excess solution would kind of collect on the base of the comb, which helped to keep the sections from being saturated. And while my hair was a little snarly before I brushed and combed in the solution, it became smooth and easy to comb thru once the solution was applied.
A lot of people talk about the fumes but they didn't really start to bother me until I was almost done with applying the #2 lotion. My eyes did start to sting a little so I left the bathroom for a few minutes, and came back to finish.
The hardest part was drying my #2 coated hair with the COLD air setting on my dryer. I see why the instructions say not to "saturate" the hair. I got mine about 75% dry, and then decided I'd just let it air dry while I ate some soup.
Finally, it was dry, and I sectioned it into about 8 sections (vs. the 4 they suggest) so I'd be sure to flat iron everything.
The instructs say to flat iron a section near the root to about 1/2 the length about 8 times, and then do the remaining half about 4-6 times. With short hair, this was a little challenging because your the top half by the root gets HOT to hold while your're working on the lower half. Oh - and the steam is normal.
Then, after all that, you rinse all the solution out (and WOW - was my hair ever straight and smooth), and condition it with the #3 solution for 5 minutes. After 5 minutes, my hair was soft and smooth, but still a little rough, so I grabbed a small squeeze of another keratin conditioner, and ran that thru, and my hair got a little bit softer.
I don't wear my hair blow dried; instead, I wet set it. So I put in a little Infusium Leave-In, and rolled it up.
When it was dry and I unrolled it, I could hear the angels singing.
This is MUCH better than a relaxer! Just make sure you flat iron your edges, and do small sections so you get all the pieces.

I used to pay several hundred dollars to do a keratin treatment in the salon. I stopped because of the cost. A coworker suggested this and I tried it today. My hair is normally frizzy/wavy/curly. It takes a lot to blow dry and straighten it daily. I applied the treatment after watching the video. It took a couple of hours from start to finish. I did do it in a well ventilated room and it was strong at times but manageable. I am very happy with the end result. I will update after a few weeks to see if the effects are long lasting.