This is a PCIe Bracket for mounting an LSI SAS 9300-8e in a Full Height PCIe slot.
I found it worked really well printing it with the little notch required for the SAS connector facing up an using supports under the bracket and inside of the connector. Due to the design being very thin I advise to print from a stiff material. I printed it in PC since it is rather stiff and doesn't suffer from heat comming from the HBA.
The author marked this model as their own original creation.