Nitecore's NPB4 is the Hummer H1 of power banks. The 20,000mAh power bank is both waterproof and impact-resistant. Designed for the outdoors, the Nitecore NPB4 is a tank of a battery pack. The power bank can be submerged up to 2M/6.5ft and it's housed in a fire retardant shell that is both impact-resistant and can withstand high temperatures.