The Decklink Quad 3G-SDI Mezzanine Card for Decklink 4K Extreme 12G from Blackmagic Design is a replacement for the original daughter card that came with your Decklink 4K Extreme 12G PCIe board.

The daughter card features four BNC connectors that support 3G-SDI. The four connectors are grouped into two input and two output connectors that work in conjunction with the four 12G-SDI connectors on the main board. Replacing your original daughter (mezzanine) card with this one expands your cards input and output capabilities.