I use a Deuter 30 ltr for day hiking, I bought it in 2012, and have walked 1000,s of miles with it since then and it’s still as good as the day I bought it , it has an airflow system which stops your back from sweating , it’s very comfortable ( I hiked 110 miles round Cornwall in a week and didn’t have sore shoulders or back,) it also has an internal zipped flap so you can separate it into 2 compartments with a zip to access the lower area separately , so you can get easy access to waterproofs food etc without unpacking the whole bag. They are a great bit of kit and not hugely expensive