I've been using a USB OTG adaptor and a normal USB drive for a while now but it was a clunky solution and had an unreliable connection. It's easy to bump and then corrupt a file mid transfer, which was also painfully slow. This flash drive is my solution to not having a micro SD slot in my phone and wanting a simple bit of storage that I can use everywhere. I anticipate travelling with it and using it as my main USB drive simply because of the ability to move things between my phone and computers so easily. It's very small and hangs off my key ring; the device has a small metal loop for this purpose but there was no string loop included. The dimensions are 27.5 x 16.5 x 8.5 mm at its largest points. The colour of the flip cover is smokey grey with a brown hue.
I found this drive at the local tech store for $25 AUD. It comes in sizes from 8GB - 64GB, and there is a USB 3.0 version also available. The build quality is decent, though the micro USB plug looks somewhat fragile (you can see a gap in the photos). Considering the notoriety of micro USB this worries me a little bit. When plugged into my phone it sits well and feels safe. It is small and easy to ignore, but this will also depend on where the micro USB port is on your phone. For my OnePlus One it sits happily at the bottom. When the device is unplugged from your phone the smokey cover protects the micro USB side. The way the device's cover flips up is a bit awkward, if you have the flat side of your micro USB port on your phone on the bottom of your phone then the little cover will face down into the surface your phone is sitting on. The way the OnePlus One port is oriented the cover stands up in the air (as you can see in DSC_5423). You could easily remove the cover, possibly without damaging anything, but this would leave the micro USB port exposed, so I probably wouldn't advise it unless it was really inconvenient.
Transfer Rate Minimum : 18.9 MB/sec
Transfer Rate Maximum : 27.3 MB/sec
Transfer Rate Average : 25.4 MB/sec
Access Time : 0.6 ms
Burst Rate : 22.7 MB/sec
Usb Flash Benchmark
Read: 29.13 MB/s
Write: 11.82 MB/s
A1 SD Bench Accurate (OnePlus One)
Read: 19.91 MB/s
Write: 14.90 MB/s
PC > USB 1GB file write: 13 MB/s
USB > PC 1GB file read: 20 MB/s
Phone > USB 1GB file write: 13 MB/s
USB > Phone 1GB file read: 20 MB/s
All considered, I'm pretty happy with this little USB drive. It's very convenient and the speeds are adequate. I look forward to USB 3.0 C type devices, with a better connector and faster transfers.