I bought this product as I thought it would suit me better, than using a hard plastic bottle. It's comfortable to run with, but when I came to use it (ie. drink from it) I was unable to release the cap, apart from succeeding in it coming off completely! I contact Runderwear who told me it was released using teeth, but I have been unable to do so this way either, and I still have not had a reply from Runderwear about a potential cap replacement. I can't currently rate it more than a 2, as I have not been able to use the product (including for a relay race I had hoped to use it for), so the rating is based on comfort to run with when full of water and for its sustainable credentials
This was surprisingly small. Fine for a shortish run. Very flexible so it can squashed into a running belt.