After purchasing a Microsoft Surface Pro 4 during a Christmas sale, I realized that the although the tablet is a great computer, the battery life is less than stellar. I needed a portable power charger to charge my tablet and my cellphone and other gadgets. The problem is that most tablets charge via USB ports, whereas the Surface Pro 4 needs an A/C outlet. I looked at a lot of different chargers, but the ChargeTech was one of the only ones I found that had a USB and A/C slots for charging. Over the Christmas holiday Amazon had a sale running on all the ChargeTech products, so I purchased the 27,000 model since it was such a great steal. The unit itself is larger than the numerous USB chargers on the market, but it's not obnoxiously large. It's still very much portable and I can slip it in and out of my laptop case with no problem. Be sure to plug the unit into a power outlet and give it a full charge before taking it on the road with you. I gave it a real world test while visiting family over Christmas during the crazy flooding in the south. The lights went out one afternoon and I was able to quickly charge my cellphone and fully charge my Surface Pro 4 with no problems at all. Getting a full 100% charge on the Surface Pro 4 and my cell phone did use most of the power, but I was happy that the ChargeTech did it's job in a real world situation with no problems. I'd recommend this charger, but I'd recommend getting the largest capacity battery charger you can get (the 27000 model) and wait for it to go on sale. When you're in a situation with no power at all, you want to make sure you can get a full charge on all your gadgets and this unit can do it!