Coolup Slim One 2000mAh Air Portable Charger external battery charger Power Bank (only 4.5mm, Unibody Aluminum Housing)

Size, shape and weight are great! But some "buts". Seems best for charging nearly dead phone, not topping off. Slow charging when topping off. Recharge time is long. Seems very temperature sensitive...had charging stop several times trying to charge phone while in my pocket on a hot day. Description on Amazon was not explicit that only output was micro-USB (tho I should've figured it out from the size and photo). This last is a bit of problem for iPhone users as it requires either clunky adapters or a seemingly rare micro-USB to 8-pin "lightning" style cable. I've found only one such cable and while it works is kind of cheesy. I'd say best for emergency use (dead phone), less good for extending phone use on a long day.

easy to fall offpoor battery

This works like all other power banks: You charge it then use it for backup juice for a multitude of devices. I've had many battery packs, some around 20,000mAh, which are bricks as one would expect. This charger is quite small but still packs in 2000mAh, which is enough for a full charge for iPhone 6. For comparison purposes, see the short list below (device/battery capacity in mAh):iPhone 6.....1,810iPhone6+....2,915Galaxy S5...2,800iPad Air 2....7,340Kindle Fire...4400Don't expect lightning fast charging with this device for iProducts. It is still fairly quick - about a percent per 2 minutes. Also, I never count on 100% capacity for any battery pack. I typically take 85% as a threshold, which for this unit would be 2000x.85= 1700. It is conservative, but figure on losing some energy.Included in the box is a leather billfold with three stickies to adhere the bank, a mUSB to mUSB cord, and adapter from mUSB to USB (female) and an adapter from mUSB to USB (male). The company sent a promotional sample for evaluation without promise of a review.

nice and compact

doesn't stay charged for very long :( I barely use it now.

Great product.

Your browser does not support HTML5 video.  (I received a free sample for an evaluation and honest review.)The video shows off both the 2000 and 3500mAh versions of COOLUP's Slim One line. They both come with all required accessories (except for an AC charger, but most battery packs don't come with one), and they also come with little wallets to carry the pack and cash/cards/whatever.The name should give this away :), but these are incredibly thin for a battery pack. It's one thing to see it in a photo, but it really did impress me once I had them in hand. I have other "thin" packs (one of which I show in the video), but these just blow them away in terms of size. Very impressive. The awesome form factor and how they still included standard features are the reasons for me giving this five stars.The thin nature of them does lead to limitations. First, the capacity. These definitely aren't the highest capacity on the market, and with the current pricing (this 2000mAh version is listed at $25), they aren't the biggest mAh/buck out there. Also, a regular USB port won't fit, so they a single input/output micro USB charging port. Personally, I'm not always interested in the highest capacity for the price - I'm willing to pay extra for a nice metal case or a form factor that I like, and I really like this form factor. In regards to not having a full-size USB port, these come with the proper cable to use with them, as well as two adapters to make it easy for you to use other cables if you want. Because I need to pack along a cable with me when I bring my other battery packs, it's no inconvenience to me to bring this cable instead. The only hitch will be if you forget it, as your friends/family will probably have spare charging cables that use a regular USB plug.The wallet that comes with this 2000mAh version is actually pretty nice, if limited in capacity. It lets you slip the battery into it, but there's nothing but friction to keep it in place. It also has a sideways slot to hold cards/cash in addition to the battery, but probably only one or two cards.Charging output is listed at 1A, and input at 800mA. Not the fastest on the market, but definitely in line with other smaller battery packs. It also has standard indicator lights showing the level of charge remaining (four lights).The metal case on the "silver" version is robustly made and feels totally solid. It does show finger prints easily, at least on mine, in that they show up as dark smudges. In the past, I've experienced that on aluminum pieces that haven't been completely cleaned of the machining oil, so that might go away the more that I use it (but I did try cleaning it off pretty good, and I still get the smudges).Overall, given all of the nice qualities of it - especially the amazing thinness - I think these are worthy of five stars. At the current price, I'd definitely say only get one if you really want the slim factor, as there are other fairly small packs that hold more and cost less. If you want slim, though, these are an excellent choice.