Ultralight High Vis Raincover XS (10 - 20L)

Guten Tag,
Ich benötige für den Flap Jill Pack Damen noch eine Regenhülle. Passt XS oder ist das zu klein?
Vielen Dank

I have just bought the Osprey Tempest 20 bag and want to get a rain cover. Am I best getting the XS or the S as the pack is 20 litres so both sizes cover it?

Would this raincover (XS) fit the Daylite Plus backpack, or should I rather buy the raincover S?

I found this a pretty good fit for my Talon 11. Its a tiny bit baggy but I have only used it so far on a. very lightly loaded pack so its nice to know it has a bit of slack for when the pack takes more load. There is a toggle to adjust its elasticated edge so it can be done up a bit tighter for a small pack like the Talon 11. Its definitely waterproof because I was caught out in a torrential downpour for about 5 hours on open ground and it did keep the pack dry. How I wish I had been wearing waterproof myself or was small enough to fit myself in the pack :).
It fold away in its one sewn in bag so can be stashed out of the way when not needed. I'm happy with it.

I originally puchased the recommended small sized hi-vis cover but found that was far too baggy for my Talon 22 (previous version prior to the new 2017 model). I felt it was about 3-4 inches too tall for the rucksack. I have since changed the cover for this XS (10-20l) version, which I feel fits the Talon 22 much better, even when the bag is well filled, maybe the sides are gaping slightly, but I feel that is a better compromise to having loads of excess material flapping about in the wind. I may "modify" my cover with an elastic strap half way up the cover to help (I had a middle strap on my old rucksack's cover by a another brand, found it really useful for stopping the whole cover coming off when only opening the top zipped part of the bag). Colour is also now called "Electric Lime" and is more of a green colour than the hi-viz yellow shown in the website photos, still pretty bright and visible though for cycle commuting.