Folding Rear BUIS - A2

Would like a folding rear BUIS that utilizes an A2 sight; might be interested in trying the CSAT at some point in time.

I find the-
Midwest Industries ERS
Yankee Hill Machining Flip Rear Sight and A1 Style Flip Rear Sight
ARMS #40 and #40STD

Any others?
I’m sure there are more than 5.
People that have used them, what do/did you think of them?

Thanks,
Greg

eta: Forgot the GG&G A2 and spring activated version.