My comment will be a double review.
a) About these batteries, which although they say they have 4000-5000 mAh as shown in their description, even both of them together are not enough to charge my phone, which has a 5000 mAh battery.
b) The XTAR charger that also charges these batteries has many issues, such as the USB-C connection not fitting well, and it often cuts out while charging. As a power bank, I would not recommend it; it will let you down. In short, neither the one product (batteries) nor the other product (charger-power bank) was what I ultimately expected.

The best batteries for vaping as long as you draw up to 10A.
Calculation is easily done with the mathematical formula and based on the watts and resistance.
Don't listen to 'up to 25 watts' etc. because it's not true, and you end up buying batteries with a higher maximum discharge capability in amps (which you don't need) and thus lose capacity.
For example:
I, with 0.69 resistance and 30 watts, draw 6.6 amps, which the battery handles with ease.

Supposedly, I bought this battery for my electronic cigarette as stated in the description, while the actual battery differs from the one in the photo since it is written on it that it is not for electronic cigarettes!!

I have had them for over a year and I am quite satisfied. Some comments say that they don't reach 5000, but I have never found a battery that reaches what is stated. Indeed, all the ones I have reach 4300 to 4400. I have been a MTL vaper for 5 years. They last a long time and so far none of them have presented a problem. I have bought at least 7-8 so far and I will buy again soon as all my mods are 21700. I don't know if they can handle high wattage. I hope I helped.

After 2 months, their capacities (4) are completely different with exactly the same usage (discharge every 2 days at 3V), something I haven't seen in any other battery: 4200, 4300, 4500, 4700.

After another 2 months, the batteries have dropped even further and the 'best' one charges with 4300mAh, while all stabilize at 4.11V.

Very good and durable battery, it lasts me 2 days and some hours in mtl. Constant use in hand almost.

Today I received and I am charging. In two weeks, I will come back if they are durable. :)

Update: I would not buy them again. I expected a longer duration, but no...

After 4 charging-discharging cycles, it only gives me 4300mAh!
Charging with Nitecore charger and discharging with flashlight on medium setting.
What can I say... maybe I got a defective piece...

With light use, they last up to three days on MOD kroma 217 with INNOKIN ZLIDE 5ML atomizer! Very satisfied.

Indeed, they also arrived to me with a 25% discount, despite the message stating "Not for vape" even though it is mentioned in the description that it is suitable for electronic cigarettes. Personally, the fact that they were at 25% off doesn't bother me because they will charge. The purchase of them together with 2 18650 batteries at 3500 came carefully packaged. Time will tell.

With the money you will get, it is better to get the 21700 T40 Samsung, which is better than this one. It does not have good performance. Get the 40T Samsung instead. Not even this one that claims to be 5,000, it's all lies. It's not worth it

2 21700 batteries inside a special charger case + powerbank manage to charge my 5500mAh phone to 90% very quickly. I highly recommend them.

To avoid speaking subjectively, in terms of days, etc., in comparison to the Samsung 4,000 at 15w, indicative numbers are as follows:
Samsung 4000: Approximately 570 puffs on average.
Samsung 5000: Approximately 700 puffs on average.
In my personal opinion, it is worth it.

The battery gets one star and a bad review as it was purchased with about 25% charge and did not even accept the first charge. Dead on arrival. Obviously, I was unlucky to buy a faulty piece, but this is my own experience. Its name does not justify such quality.