USB On-The-Go, or just OTG for short, is a specification that allows USB devices like digital music players, smartphones, tablets, etc. to act as a host for attachment of USB peripherals such as memory card readers, USB flash drives, and other peripherals. With OTG compatibility, your smartphone or tablet functionality can be expanded beyond it's out-of-the-box capability. SD/microSD USB OTG Card Reader and 3-Port USB Hub. Works with OTG compatible Android 4.0 devices including Galaxy S4, Galaxy Tab 3, etc. Supports SDXC and microSDXC cards up to 64GB (32GB in OTG use). Perfect for adding storage or moving files between mobile devices and flash memory. Add USB storage and/or keyboard & mouse.