Principle class devil in the details

Great idea, backpack and bike bag to combine. "Conversion" is quick, plenty of storage, good layout. Everything included what you need no matter how (helmet holder, rain cover, adapters for different Porter "diameter"). Wears as a backpack well (of course not for 20kg suitable ...)
But be careful in the hub where the backpack as a pannier rests below. There the material Schubbert quickly (a smidgen degree or rough areas such as on the screws of the rack for rich already made).