If you sometimes have trouble deciding which extra t shirts to take along or whether you should take two pairs of shoes or three you may want to switch to ortlieb because the worlds largest waterproof bike bags have plenty of space for everything you need the back roller pro plus is the xl version of the popular back roller plus touring bag with a volume of 70 litres per pair it offers almost twice as much stowage space its also the first ortlieb back roller with an additional front poc