I love this pack. I’ve used and abused it for about two years and it has coped with everything that I’ve subjected it to. It is wonderfully light and very packable.
You can use it as a daysack as it is easily large enough to carry the kit needed for a bimble. In fact, it is large enough to carry enough gear for an over-nighter in summer. It also works as a stuff sack inside a larger rucksack and then it can be used as a daysack when basecamping. Mine has carried shopping, library books, clothing, guitar gear and lots of other things without failing once.
There are drawbacks. The pack isn’t totally waterproof but it can withstand a prolonged shower, the straps can loosen, you need to insert a piece of foam to cushion your back and you have to be careful how you pack objects with sharp corners. Nothing serious though and easy to cure.
After nearly daily use for two years my day sack has developed a couple of pinprick holes but it is still usable. It is also repairable with a few dabs of Silnet glue!
The Sea to Summit Ultra Sil 20l day pack is an excellent choice for anyone who wants an ultralight day pack.