Power banks are a great backup when you can’t get to a charger, but not all of them can take a beating like this brute.

The UNIFUN U821 power bank has been around for quite some time now, but only recently did I have a chance to get my hands on one to see just how good this thing was built and functioned. Although 10,400mAh isn’t anything spectacular in terms of backup battery life when compared to the likes of Vinsic’s 20,000mAh power bank, it’s the rugged construction and waterproof design that makes this option ideal for outdoor use.