A:Answer The card is very small and is made to directly fit into your device. The SD adapter is used, for example, if you want to use a SD card reader on a computer or on a stand-a-lone SD card reader which has a larger interface slot. In that case, you put the micro SD card in the SD adapter and then put the SD adapter (with the microSD card inserted) into the slot of the SD card reader. Remember, it is a microSD card you are purchasing. There is also a memory card called an SD card which is much larger in size - thus the microSD card to SD card adapter.