When you are out and about you need a backup just in case your battery dies suddenly or over time. This should be good enough to back you up when you need to get moving from a drained battery. It has four bars for intervals of 25% each. There are 4 bars that are in total(25*4=100%) full battery. Ports to charge other devices such as cell phones, just in case you have "2 emergencies what else could you ask for. Oh yes, it is light and compact.