Very nice, but not for 20 degrees.
These bags were comfortable! My husband and I both got one. He is 6'3" 195 and fit well though he is unable to "curl up" at all in in as far as curling up within the bag to draw legs into same air space. I, on the other hand, could curl up into same air space if I wanted at 5'6" 134.
We slept in a hammock without a pad. On the first night with temps into mid 30's and wind, I FROZE (well, my feet froze. my body was ok). I'm sure this is a combo of the hammock angling up at feet so blood drains, feet in small air space, and no pad. But still, on it's own, this bag is not enough at that temp. The 2nd night, I stuck the feet into my backpack lined with a backpack rain cover and an extra tshirt. It was much better. Overall, great bag. Just get a liner or pad or something if using it below about 40-45.