The combination of portability and capacity makes it so that you don't need a large bag or a small bag to carry it in. Portable chargers can charge your electronics without the need to put a bundle of extra weight in your travel bag.
If you are looking for a portable and durable high capacity charger, then the iMuto 20,000mAh portable charger may be the one for you. If you are a big outdoor fan and want a reliable power source in a remote location, the ZeroLemon 26800mAh portable charger is the best choice.
If you are looking for a good travel charger dual USB for the iPhone, this power bank with 20,000 mAh is able to charge one of the new iPhones several times. If you want to use this as a power bank to charge your phone, you should get a portable charger with more power. However, if you only want to charge your iPhone, iPad, iPod touch or other portable device, a portable 12W or 18W charger should be sufficient.