Does restrict flow but more difficult to put on than expected - takes away from the moment.
I would suggest just the single loop as the double is hard to get tight enough for good effect without pinching skin. Ended up just taking off the second adjustment slide. The silicone is thick enough that it doesn't "cut" into the skin. Having wife help made it easier - was able to get it tighter without pinching. Overall - what I expected but was hoping for more