I have bought an Ultra Compact Power Bank to replace my existing power bank. My original Power Bank was 20000mAh which I had bought four years ago. It got considerable use and now no longer holds a charge. So, I knew I needed a replacement.
This one was smaller at 10000mAh, but it was also a lot smaller and importantly lighter as well. I also like how it came with included cables.
My main use case is when travelling with just my phone or attending a conference with just my phone. If I have my laptop with me I can usually use that to charge the phone. My phone can usually hold a charge for most of the day, but I have found now and then something I am doing kills the battery.