Obrien boards come from the factory with a stud you insert in this fitting, then you simply thread a standard GoPro tripod mount on top. I recommend a rubber washer between the board and mount to help dial in placement. If you're missing yours, reach out to Zach at Obrien Customer Service - ZachS@Obrien.com
, tell him Ross sent you and what you're looking for, they might have a few laying around. Obrien did stop including these mounts on the majority of their boards in 2015 so if they don't have any left over, email me at firstname.lastname@example.org
. I have a few extra laying around I'd be happy to send your way at no charge.