Kindle / Kindle Fire is micro-USB, there is no doubt about it, and no there are not different shapes/sizes of micro-USB.
I've owned / modded a number of Kindle / Fire devices, and can tell you that for regular communication between a PC and Kindle / Fire, a standard micro-USB will do it.
The only thing you need a different cable for is if you need to get into 'fastboot' mode for hacking / modifying the ROM on your Kindle Fire, the pin-outs on that cable are different.
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I've owned / modded a number of Kindle / Fire devices, and can tell you that for regular communication between a PC and Kindle / Fire, a standard micro-USB will do it.
The only thing you need a different cable for is if you need to get into 'fastboot' mode for hacking / modifying the ROM on your Kindle Fire, the pin-outs on that cable are different.