I use a standard umbrella adapter with a 1/4 20 male post on it. The speed ring has 1/4-20 threads on one of the sides, all of my speed ring have it so I assume that they all do. I just screw the umbrella adapter into the speed ring. Here's another look at, just a bit closer.
When it comes to attaching my strobes to the speed ring, I simply use a "Justin Clamp" clamped to the ring. I use this method on all of my Octa's as well.
I hope this helps. DT
Wanted to also show another style of umbrella adapter. This is one from B&H their impact design. Here I'm fitting a speed ring which is designed for a Dyna-lite strobe head. Hope this helps. DT