This is a low-profile bracket for the Mellanox ConnectX-2 single port 10Gbit card. You can find used cards for dirt cheap on eBay, but they usually only come with full-sized brackets. The bracket may work on the other Mellanox cards, but I can't confirm this.
Finding low-profile brackets for this card was nearly impossible when I first decided to design this bracket. Thankfully you can find some on eBay nowadays.
You will need to print some supports for the edges. If your slicer isn't generating the supports properly, then try rotating the part on the z-axis and try generating again.
You will need to tap the card mounting holes. It's plastic though, so you should be able to 'self tap' by driving the screw straight into the hole - no tap and die necessary.
Designed in FreeCAD 0.16
You can change the size and position of PortCutout if you want to try making a dual-port card.