Pretty sure they are Gleichauf. I had a pair, but I did not use them. I was TOLD(which is not the same as personal experience) that they were the same as Byron fans, maybe a little more efficient, thrust and revs should be very much like Byron.
I HEARD, also, that their F16 was a knockoff of the byron, and flew just the same.
If you are building a twin, I suggest you set up a test bench and check out those R90s...me, personally, would not feel good about the reliability of those, particularly in a pair.