It is a camera adaptor, not a full OTG device. So most USB flash drives will say, "can't use as this accessory draws too much power." So if you buy it as a camera to iPhone/iPad adaptor, it will work 100%. If you use it for other things, it may or may not work. e.g. I've seen people put the Audioquest Dragonfly DAC on the end of it and that works fine