Under ArmourWomen's Tech 1/2 Zip - Twist T-Shirt

I tried purchasing one of these in Costco (which are cheaper than online) but unfortunately they do not stock many small sizes and I missed the boat.This is a brilliant thin, long-sleeved sports top which is close-fitting. It is not lined and has a front zip fastening part way. The collar is high. It can be crumpled into a hiking bag and does not take up much space at all. It is surprisingly warm too. This is just perfect for an all day hike when the weather is a little cool prior to the day warming up. I am currently wearing this over a tshirt.It washes well.

Fits me perfectly - I bought a small and am a UK size 8 - and is really comfortable and lightweight. I like that it is a little longer length in the body than other brand tops of the same style. I wear it for hiking and also for leaving the gym after a workout and it's great for both. The long zip makes it easy to put on and take off without needing to redo your hair. It's great worn on its own, over a tank top, or even under a jacket.

Buy your usual size.I went up after reading reviews however I had to return and buy my normal size as it was way too big.I usually wear size S or 8, sometimes XS with UA.This I bought size S.You don’t need to go size up or down(unless you want it to be tight on your body)

I love this top, it's warm but still breathable, fits well, washes well and allows me to exercise outside without a heavy jacket. Can also be used as base layer under a fleece

This was perfect for what a I wanted - it's very lightweight. I get super hot quickly so didn't want something thick. Will be good for me to as low as 5C outside - might be too lightweight for some though. I am a medium in somethings and small in others. This definitely fitted and it's a medium. If you are looking for a looser fit - go up a size.