Cool and protected! - Rab Aurora Pull-On Jacket - Women's

I have worn this twice and washed once, and so far it seems to be a high-quality garment. The sleeves are nice and long (so long that they cover my hands easily without needing a thumbhole to keep them in place), the material is slightly stretchy, extremely lightweight, very breathable and keeps me cool even while sitting in a hot car in the sun.
I really like that it is UPF 50 (I need at least UPF 40 if I'm to be outside for more than an hour) and that the hood covers my neck and ears (otherwise I'll get a rash after being a few minutes in the sun); the hood is also tapered enough to be able to fit easily under a bike helmet (but would also stretch to accommodate a pile of hair underneath depending on your needs).

Since this is a pullover and not a full-zippered jacket, I would recommend sizing up slightly for a little extra ease in pulling over your head. The front hidden pocket (on the left bust) is somewhat awkward, but you don't have to use it.