AYBL (gym brand) sport shirt in a crop top cut. 
The long sleeves also have a hole for the thumb. 
Unfortunately, the shirt is a bit tight on me (normally I wear size M). 
On the back, there’s also a small opening (so you can see the sports bra, if you have one and you wear it). 
I didn’t wear it often and the material is really good quality (not cheaply made). 
Purchase price was 34.–