Not much volume, fits Galaxy S3 Barely, but a BT receiver for it for better performance
920361
This thing works fairly well but it has a few issues.  I'm using it with a Galaxy S3, and it barely fits in the waterproof area - I have to take the phone out of it's case to fit in.  if you've got a Galaxy Note or something similar forget it - it won't work.

The sound is OK, but there is very little base, and it's barely load enough to use outside.  It's ok for personal use sitting next to it, or on a small boat, but it's not the kind of volume that can be heard above any sort of constant background noise.

The speakers in the housing are very small - maybe 2" - what's seen on the outside of the base are just plastic covers.

I'm using mine with a Bluetooth receiver inside instead of the phone - $20 around amazon.  Much less hassle if you don't need the waterproof feature.

The external controls only for work pause/play on the S3. Next and back don't work with Pandora.  Maybe with a player they might work.

There's not much else around like this device, and it's super rugged and the batteries last a while.  It's nice, but don't expect load volume or it to fit your device.
2354988
Tinsy sound.  Bluetooth works, but speaker is more super annoying than superloud.
1786326
Pros:
looks nice, smooth, modern design
usb port for charging phone
bluetooth for playing music without cables(upto 40ft connection)

Cons:
too small to play loud music
plays music not much louder than Galaxy S2
usb port is in bad place -  I think port will be damagade if you would disconnect phone every day like me and you have to remove all protective cases to fit into port
should cost less to be fair

My opinion?
I'm going to return this product for full refund and buy normal computer speakers with front jack for my phone to be able to play music.
1908484
The audio volume output of this receiver is extremely low. In order to hear music through my car stereo, I have to turn the car stereo volume up very high--so much so that you start to hear static and the overall quality of the sound seems low. I wound up going with an Anker receiver instead, and that works perfectly.
215247
Used it with a class d amp to make some small bluetooth speakers, since my chromebook just doesn't have enough gain.
Boops and bleeps and other bluetooth noises (40 or so db down but still...), not worth it for my use.
4955391
I was surprised how small it is (about 5 inches).  It's loud enough but not much more bass than my phone's speaker.
1904143
I got mine for just over $10 including shipping. It works great streaming music through my Samsung Galaxy S3 through this bluetooth adapter into my cars auxiliary port. The music sounded better than the radio.
4634962
It isn't terrible, but the bluetooth range is pretty low. Don't expect to have your phone more than a couple meters away from the speaker if you want a signal.
4890550
It sounds good at lower volumes, but it is a little bit tinny sounding. Its still usable though.
4928762
This little Bluetooth FM Transmitter is just alright.  It allows me to play music from my phone via Bluetooth on my car stereo, but the sound quality is not great.  Its like a typical FM transmitter that always has some static and doesnt give you all the bass or treble I have come to expect on my Bose car stereo.  Unfortunately, my 2009 vehicle does not have Bluetooth capabilities built in or a single pronged AUX input, so I was limited that I needed to use an FM Transmitter in order to get Bluetooth in my car. Additionally, I bought this one in particular because it came with a cord that allows you to use the headphone output of your phone as a direct input to the transmitter - a great functionality when the Bluetooth on my android phone is not wanting to cooperate (a common issue with S4/S5).  Unfortunately, I could not get that feature to work.:-(  I do like that it has dual USB charging capabilities.  Overall this serves the purpose, and it is inexpensive, but you can find more quality FM transmitter Bluetooth solutions for not much more.  In particular, I found another one that worked better and you can find my review of it here https://smile.amazon.com/review/R19NOSO0Y7LMOQ/ref=cm_cr_rdp_perm

I received this product at a discount in exchange for my honest and accurate review. I regularly use customer reviews to help me make informed decisions on what products to purchase online and want to help others do the same. Happy shopping!
3455741
but it doesn't has the same gain as the airplay option. you need to increase the volume a bit more while you are on bluetooth streaming.
4442500
It's OK.  works fine. decent Bluetooth range and battery life.  Not very loud and doesn't have a lot of bass for it's size.  I ended up buying a smaller JBL speaker which is loader with better bass and much smaller.  about twice the price but well worth the upgrade.
621197
It is okay but just barely.
TOO LOW sound volume.  It is okay for system beeps and so on, but not any good for music or other uses.

I do feel I got what I paid for, and the USB connection is convenient.
If you want full, normal sound I suggest looking at other models.
btw -- it installed without a glitch automatically.  Just not enough sound volume.
754033
Decent. Not great sound but what can you expect from a speaker the size of a tennis ball? It isn't much louder than the speaker on my LG G3.
1294759
I like the Bluetooth and slim design.  Only issue I have is that the speakers are really bad.  You can't turn them up at all and expect good things.  This unit is pretty much for easy listening at low volumes.  If you like to turn it up or have a big space to fill, look elsewhere.
4264595
I'd read the reviews and was expecting mediocre sound. But it's worse than that. For talking on the phone, it's acceptable. But for music and/or radio listening, it's like a cheaply made transistor radio from back in the day. I do, however, like the ease of powering on and off and connecting the headset with my phone. Installation was fairly easy, as well.
4083504
Works well, I use it as a receiver for car, but for headphones, there are better options