This portable backup battery is great!
Theoretically this should charge my phone battery (Samsung Galaxy S4, 2600mAH battery) about 7 times, however from normal use and real world losses this Power Bank charges my phone about 5 and half times. However when re-charging, I'm usually using the phone to some degree so you could say there is some level of equal input and output of power.

A backup bank that charges your phone 5 or 6 times with one charge is still very impressive at this price, and I will continue to use and recommend this device.

For what it is, its not as heavy as I thought it would be, and its just about the perfect size. I keep it in my backpack at all times so it's ready to be used. The build quality is great, and feels like a quality product.
I've already ordered a second one and a third may be in the works

You could kill someone with this this, it's that heavy. But I guess it'd have to be with how much juice it holds. It also takes over 8 hours to recharge, which I think is crazy. I would have spent extra to get an actual percentage of remaining power is left on the unit.

Note:
I put electrical tape over this bright light that comes in when the unit is powered. Not needed since the power button also lights up. Not good on a dark plane.

This thing is amazing. It kept 5 peoples phones charged for a full day at Disneyland. We were using multiple apps all day long and the phone batteries got quite a work out between Pokemon Go, The disney app to check the lines at both parks, texting, and many other time killer apps. Even when it showed red, it was still charging the phones. Can't say enough good things about this battery pack, other than it is a little heavy, but for that small penalty you get the comfort of knowing you will always have a charge for your phone, and others as well.

Works as well as advertised and at a very reasonable price in comparison to other brands. It takes about 10 hours to bring to full charge. I took it on a 3 day camping trip and was able to charge my phone from about 20% to 100% 4 times plus recharged my bluetooth speaker 2x and it still never got to the blinking indicator of being low.

Hello,
Lets begin with an intro, This AUKEY power bank has a capacity of 20,000mAh and sports a micro usb slot to "recharge the Device" , 2 usb slot to charge android and apple devices and a Lightning slot for apple devices.

Pros:
1. The Device is a nice size not overly bulky. Here is the weight and dimensions. Dimensions: 5.9" x 3.26" x 0.8" Weight: 13.7 oz
2. The speed at which this devices charges is excellent compered to a regular 1amp wall charger.
3. Built in Flashlight
4. Comes in Relatively nice packaging.
5. Seems Durable but I wouldn't test it.

Cons:
1. The charging indicator, Shows green for "90%-100%" power, Shows white for "89%-20%" power, and Shows red for "19%-1%" power. In my personal opinion I like a "light series indicator" or a "LCD screen" (Makes it hard to know what percentage its at)
2. Takes about 4-6 hours to charge to full capacity.

Overall: I am very impressed with this portable charger, its "pros" definitely out weigh the "cons" in my opinion.

Comparison: Compared to other chargers in the same category like the RAVPower, or Amazon Basics chargers, I would chose the AUKEY.

AUKEY 20000mAh 3.4A Dual USB Lightning and Micro AiPower Portable Charger