The Back Roller Plus from Ortlieb is a well-regarded pannier among the cycle touring community. Although potentially less durable than the eminently recognisable Back Roller Classic the Cordura fabric of the Back Roller Plus can certainly take some scrapes and we think that it would stand the test of time on longer tours.
Our stuff was kept dry even in heavy and sustained downpours thanks to the waterproof Cordura and simple but effective roll top closure system which combine to create an IP 64 waterproof rating.
The rack fixing system is easy to use, quick release clips work without and dramas and, being that they're supplied with extra inserts to suit the diameter of your rack are tight and stable. A simple but effective rotating clip on the bottom of the pannier adds further stability and has enough adjustment to fit most shapes and sizes of rack.
An inner pocket and mesh zip pocket allow you to stash smaller items away from the jumble of other gear and the strap doubles up as a securing strap for the roll-top closure as well as a shoulder strap to carrier the pannier around when you're off the bike.
The quality of this pannier is evident in its construction and it arguably provides everything you need in a rear pannier at a reasonable price.