So I went ahead and used a card that I already have for my DJI Phantom 3 Pro that I just got, I'm just wondering if it's good enough for recording with 4k, it seemed to be ok, here's the card in question:
SanDisk Ultra 64GB microSDXC UHS-I
Amazon.com: SanDisk Ultra 64GB microSDXC UHS-I Card with Adapter, Grey/Red, Standard Packaging (SDSQUNC-064G-GN6MA): SANDISK: Electronics
SanDisk Ultra 64GB microSDXC UHS-I
Amazon.com: SanDisk Ultra 64GB microSDXC UHS-I Card with Adapter, Grey/Red, Standard Packaging (SDSQUNC-064G-GN6MA): SANDISK: Electronics