This is the Original Equipment IR Receiver module that came with the Version 2 Scorpion Speed Controllers. If you lose your original Receiver Module, purchase an second-hand ESC that is missing the IR Receiver Module, or just want to have an extra in the shop, then this is the part that you need.
To see if this is the correct part for your ESC, look at the serial number that is laser engraved on the gold heat-sink plate on the ESC. If it is one of the newer V3 ESC's then this receiver will work. If the serial number has "VV2" in the middle of it, then it is a Version 2 ESC, and this is the correct part for your system. If it does not have "VV2" in the middle of the serial number, or if it has no serial number at all, then you do not need this part.