Other than that it stayed on my arm and was comfortable, for the most part
933003
Only 3 stars because I had to take my phone case off every time for it to fit. I have a GS4 and a Commuter Otterbox. Other than that it stayed on my arm and was comfortable, for the most part.
4570928
I don't know if it was just me or the velcro, but the strap never stayed on my arm for long. I would use it when I went running  but it seemed like every movement made it slip no matter how tight I strapped it (without cutting off my circulation).
2507641
This armband is very comfortable, I didn't even feel it while running. The only thing that would make this a 5 star item is if it had stronger velcro. It did not come off while running, but if I flexed too much it would pop off so I would not be able to wear this for any strength training. Other than that, the plastic still lets you use the touchscreen well, my phone fit fine with a case, and I like the key slot.
206513
Very comfortable, but occasionally falls off. Though annoying, it doesn't make me dissatisfied with my purchase.
3875
For the price I was very surprised.  the costume was very comfortable and made of good quality material.  The arm bands did not fit well though and came off or slid down my arms several time throughout the evening.
2780508
Very comfortable and secure on wrist. My only gripe is that it's a bit annoying to resize the clasp.

*Update* I had it on too loose and it fell off and I nearly lost my fitbit.  I wore it very loose on purpose and it was my own fault but I would caution you to make sure it's not unreasonably loose.
4214912
This should really be listed as a large armband.  I bought this for my daughter as she is picking up running again and wanted to listen to her tunes.  However, even on the smallest setting, the armband would not stay up.

Otherwise - there was nothing wrong with this.  It holds the phone just fine.  It is comfortable and probably works well on larger arms.
1463054
I work out 5 days a week, but as a business owner and parent I need to have my phone with me constantly. My cardio activity doesn't necessitate having my phone mounted to my arm, but since I do want my phone with me while lifting, and it was bothering me keeping it in my pocket. It kept falling out or getting in the way doing certain movements.

I like the look and feel of this holder. Sleek, soft and and it seems durable, though I won't know for a while. While it mounts intuitively to my arm, it was actually harder than I anticipated to fasten it tightly. At one point I almost asked my wife for assistance. Not a big deal, but not quite as turn key as I would have thought.

The plastic allows the touch screen to work easily. So there were no issues operating my phone. Unlike many people who like to mount their phones to their upper arm, that's not accessible enough for me. That works for a runner who just wants their phone with them. I want to actively use it. And there in lay the sole problem. I had to mount it to my forearm. I'm a big guy, but the phone is just too darn big. It's not the fault of the holder, but it just wasn't as comfortable or easily operational as I like.

So 4 stars instead of 5 because while the holder works, it's kind of like trying to keep a dinner plate strapped to your arm, LOL
3438173
usually with this bra, I don' t have any problems with the straps slipping down my arm.  Unfortunately I have problems with this particular bra, with the straps constantly slipping down my arm
266977
It did everything that it says it does except stay on my wrist. It fell off silently while I was working. I had it for about a week and didn't feel it go. Other than that, it was perfect. Using it with the heart monitor around my chest was far more accurate than the Fitbit charge HR. But the locking mechanism on my arm did not stay locked. And yes, I locked it with a twist, just like the directions instructed. So, with the exception of it not being here I would have highly recommended it. At least I still have the heart monitor.
4405033
Sometimes it doesnt want to stay over my upper chunk but its mostly fine.
592617
Controls easy to use, but arm not easy to move.
3494558
This is clearly for people with larger arms. The first time I used it I could barely keep it on. I ordered some small strips of velcro to add to it that just stick on and now it fits just fine. I'd suggest doing the same if you're having the same issue I had with it.
2995662
I have had several different arm bands and this is the first one that slips while I am running. Not sure if it's the fabric of the band or the velcro that isn't working for me.  Other than that it's good.  I liked the velcro holder for earbuds and the extra pocket in the back for cash/card etc.
1941511
When I purchased this arm band it was around $5 so it wasn't exactly breaking the bank for me. The band is made of the usual neoprene material which will get saturated with sweat as you work out. With the adjustable straps the band fit snugly on my arm and the plastic around the phone prevented sweat from getting to it. I have an average build, 6' 0" 185 lbs and the band fit comfortably on my arm. It only survived ONE workout session though because the Velcro is held on by a cheap adhesive. Sadly after the initial trial workout the Velcro ripped off from its gray attachment and now I have a broken arm band.

TLDR: Okay for the five dollars, but do not expect it to last forever and ever.
1929331
It works but it slips a bit. I run with my arms bent anyway so it's not a huge deal. It doesn't bounce around, I just just feel it slide a little. Another small drawback is when the strap is pulled tighter (to help keep it from slipping) the Velcro sometimes catches. One really great thing about it is the cord length of my ear buds tuck nicely into the armband. Keeps it out of my way when I'm runninh. I used to have to hold it.
3069200
Thanks to it, I can finally go jogging comfortably! It slides off a bit depending on the exercise, but my other one use to do the same due to moving your arm: flexing and releasing.