The AData i-Memory flash drive is a little different than your bog-standard USB drive. This has 2 ports, one USB 3.1 and one Lightning, allowing you to connect it directly to a lightning equipped iOS device.
At just 6.9mm thin and 3.6g light it is as small or smaller than most normal USB drives, and certainly small enough to carry around in your pocket when travelling.
The model I was sent is the 64GB version and this is currently priced at £60.64 on Amazon, which is quite a big premium for a lightning equipped USB. You can pick up 64GB USB 3.0 drives for as little as £20, however, other similar dual port USBs cost around the same as this. The Adata seems to be the most attractive and smallest of the lightning USB options too.
The performance of USB drives can sometimes be a little questionable, but the Adata does well. Using Crystal disk, I achieved sequential read speeds of 156MB/s and write speeds of 64MB/s which is actually higher than the quoted figures of 150/50. In comparison, my cheaper single port USB 3.0 SanDisk drive achieved 114MB/s and 45MB/s. Random read/writes drop off significantly, but this is always the case with storage. Transfering a 4GB Windows ISO file I saw write speeds closer to 40MB/s
When using it on an iOS device you will be prompted to install the required app when you can back up your files or access them for viewing. With iPhones not have expandable storage this is a great option to have, in general, I backup my files directly to the computer and/or to iCloud, but where it really comes in handy is when I travel and I can take some movies to watch. The app fully supports media playback and you can also use subtitles with it that are synced properly.
In addition to Airplay mirroring on Apple TV, the i-Memory app supports iOS mobile device content display on TV using Chromecast.
Overall, while this is expensive compared to traditional USB devices, if you using iOS it is a great little investment. It is well made, easy to use and performs great.