Received this bra/binder today and tried it on. First thoughts, it's a soft, cotton material, softer than spandex. So, a bit of background:I got this not for f2m purposes, but instead just because I like the 'tomboy' look. I'm bigger chested, 34DD, which means 38in across the breasts. I personally just like to dress more androgynous than feminine and have always hated my big chest. for this reason i tend to wear sports bras, I'm AD military, security before that, plus like i said i like a flatter chest. I wanted a bra that would minimize my chest better than the sports bras, but still allow me to work out, etc. Personally: Love it love it love it!!For f2m:Gentlemen, so far as completely flattening goes, this thing does the job better than the name would imply. As i said above, (hopefully can upload pics to illustrate) i'm pretty big chested. with this on, yes you can still see a bulge, but it looks more like pecs than breasts, even at my chest size. a smaller chested guy it would do even better. that said, it is more bra-like than it is binder like, I haven't tried on an actual binder, those may do a bit better though i can't imagine how. aIt is REALLY comfortable. no, seriously, when i put it on, it did not constrict at all. I had no trouble breathing, and it did not push on my ribs or anything. I dropped and busted out 20 pushups and sit ups, no painful breathing nothing (I would have done more but didn't want to work up a sweat before bed, lol). It was not painful under the breath or on the shoulders. I plan on wearing it all day on a day off then i'll know more long term.If you're considering a tighter alternative to a sports bra to break up wearing binders, this is it! If you want a break from binding, but still want to minimize dysphoria this is the answer.If your family/parents are not so keen/don't know about your transition (or if you're just trying things out and don't want to make an official announcement) this is also great. it comes in a plastic bag, has 'minimizing binding bra' or such in small lettering. so it looks like a sports bra and can be passed off as such.For Sports purposes:Ladies this thing is comfy. it doesn't feel like or look like it when you first try to put the thing on (more on that later) but it is comfortable. As i said above, i dropped and did twenty pushups, and it felt SO much better than in my regular sports bras. Sit ups same thing. I imagine running will be great as well, will wear it to PT day after tomorrow and post an update then. the material is soft, and it does not constrict breathing or anything.Getting on:That was tricky. it does have to be put on like a binder, for those who don't know, that's inside out, upside down, stepping into it. then working it on up your body. this is sightly awkward, a lot of tugging, rolling and messing and contortion, at least for me i have wide hips. All in all it was probably only a couple of min tops, but at first trust me, it does feel like it won't fit! Don't be tempted to try it over the head and nearly strangle yourself like i did. It doesn't work just do it inside out, upside down, and pull it and pull and pull and it'll fit. Get it off the same way, going down rolling.Fit:I measured under bust, e.g. under the breasts around the rib cage, and that measurement was accurate.Photos. the first two are of me in this bra/binder. the second two are of me in a VS sports bra. As you can see, the difference is considerable. As I am large chested, yes, you can still see breasts and if you're really looking you might not mistake them for pecs, but in a t-shirt or sweatshirt, it's pretty minimal.I'll post an update after i try wearing it all day. But so far I plan on getting a few more, I like it so much!