This was specifically designed for a 3DR Solo - it allows you to mount any camera with a standard 1/4" tripod mount on the bottom. The hole is offset so a Sony a5100 has ideal positioning once mounted. It also works with a lot of GoPro accessories and other cameras.
All you need is a 1/4" bolt (get one with wide head) that's about 10-12mm long. I just cut down an 18mm with my dremel. More info on my blog here.