I have two of them. As a charger it's almost unusable because of how slow it charges. 5V at 2A is just not enough power for a 4 slot LiIon charger. As a power bank it's fine. Espically if you have a lot of older 18650 laptop pulls lying around like I do. I don't think I would have bought them if I had to actually buy batteries them. Flat tops or button tops will fit, but protected batteries are too long.
Frank
I would say between 68 and 69mm would be the max length. It has two output ports one is 5V at 2A the other is 5V at 1A and that's it no QC or adjustable output voltage. The display shows 4 battery indicators with 4 power level indicator lines for each battery. So it's very easy to see individual battery levels.
To me it fills a very small market. Let's say you have 24 NCR18650A's that are at 3000mAh capacity. That's 72000mAh at 3.7 volts. That's over 53000mAh at 5v. You would need a whole lot of self-contained power banks to give you that much power and would be way more expensive assuming you could repurpose the batteries like I did.
Basically my conclusion is if you have a whole lot of old or recycled 18650's and a good way to charge them. Then this is a good power bank option.
Frank