FX Panthera HC bottle adapter for the rear

Hello everybody before I buy I want to make sure…I want to add rear 300cc bottle to my hunter compact which has the front 480cc already. Friend Is sending me some spare part such as:

saber tactical front bottle adapter st0056
The silver one the picture. He told me that this should also work to put in the rear I just need to remove black plug in the rear stock.

HOWEVER, should I buy FX dynamic/Panthera double air adapter kit m130 the picture with the black pieces???? Or should the silver one work for what I want to do.

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