These things are really awesome! I have tried them in a variety of flash drives and card readers and the only one I've found they don't fit well in are the Lexar Twist Turn (too tight in the TT, but they fit in a different style Lexar).
Works flawlessly with my Samsung Galaxy Note 4 with OEM Kitkat 4.4.4, my rooted Hisense Sero 7 Pro tablet running AOSP 4.4.4 Kitkat and my Nvidia Shield Tablet with OEM Marshmallow 6.0.
Ordered on April 2nd and received on the 15th. Not bad for shipping from China.
EDIT (06/23/2016): These are also awesome for use with the Raspberry Pi Zero! Use them with USB WiFi adapters, wireless keyboard dongles, or to connect a USB hub.
I'm using one with one of these $4 USB WiFi adapters WiFi Dongle for pcDuino/Raspberry Pi and it's working perfectly. The fit was a bit tight, I had to use pliers to get it out the first few times, but after a few insert/remove cycles it loosened up. On the other hand, both the OTG adapter and the USB WiFi adapter are inexpensive enough to just dedicate one to your Zero. If you edit the /etc/wpa_supplicant/wpa_supplicant.conf file on the microSD card to add your wireless SSID and encryption key, the Zero can be booted completely headless and will connect to your network automatically, then you can SSH in to control it.
I have also used these to connect a 4-port powered USB hub (OTG adapter into the USB cable from the hub). I used two ports of the hub for the WiFi adapter and a micro-USB cable to power the Pi-Zero from the hub itself. That left two more USB ports available, and I only used one outlet to power both the hub and the computer.
I recently purchased a Chromebook which only has USB-C ports, so I ordered some of the new USB-C versions of these handy little adapters, and they works great. They don't fit as deeply in the plug as the micro version, but I don't find that to be a problem. As above these only support USB 2.0, but for keyboard or mouse dongles that's fine.
Ultra Mini DM Micro USB 5pin OTG Adapter Connector for Cell Phone Tablet & USB Cable & Flash Disk This OTG Adapter is compatible with most android phones. Make sure your phone support OTG function. This adapter can only used in OTG android phones / tablets. Suitable for/Support the standard USB interface, not the thin one. 5pcs connector in the package.