I bought a XS Kinder 10L race vest and a soft bottle. I was inbetween sizing with XS/S and normally wear a UK 10 on top and have a small chest size. I’m glad I went for the XS, it fits perfectly. With more layers it may be that the front pockets are just further apart. It’s comfy and has plenty of room for storage, and it doesn’t feel like I’m wearing it. I will say that the waterproof phone zip pocket isn’t big enough for my iPhone 12 mini with case. This is quite frustrating as it means I’m having to put my phone in a sandwich bag in one of the open front pockets. All in all it’s great quality for the price!