The last time I bought one of these backup bateries it was the size of a quart of milk.  This product is small easy to use and works flawlessly, easily adapted to my Ipod and Blackberry and lasted forever or at least as long as I need it which was an 11 hour plane trip.  To be perfect it just needs an adaptor to recharge my Kindle.  My only fear is that I will lose one of the adaptors.