It's just a cheap battery, at first it might work decently (about half the capacity compared to the original) and it will last about a year (give or take). At the end of its life, it simply dies without warning.
IF YOUR BATTERY HAS DIED, GET ONE. An original battery that has worked continuously in a phone for 5 years will be better than any battery you buy, no matter how similar it looks! This is the truth, I have measured it in several phones.

If I could, I would give it a 0. I bought it and within the first week, the battery started to drain very quickly. I had to either always have a power bank with me or charge it every one or two hours. The result of this was that the battery swelled, and luckily I noticed it quickly.

For now, it works well but I haven't used it for long enough to have a complete opinion.

I bought the battery on 04/11/2021 and in a short time, the battery started draining quickly. I had to charge it three to four times a day. The battery would reach 100% charge in 8 minutes, indicating that something was not right. On 18/2/22, I removed it to put back the old battery. I noticed that the battery had swollen and had detached from the screen at one point. Additionally, the plastic body of the phone had cracked at the edge where the screen attaches. Not only was it not worth the purchase, but it also damaged my phone.

The battery was discharged (0%) and slightly damaged at the corner. The product works as it should so far, however, I received it in inadequate packaging. I will inform the seller immediately.

update 26/11/21
The battery was installed without any issues and charged normally (I left it until 91%). With light usage and Wi-Fi on, the battery is at 65% after one day.

update 29/11/21
So far, it is functioning correctly. I received it with a minor impact (which doesn't seem to have changed its properties)

Terrible, it barely lasts a day with moderate use. Do not prefer the bulk version. The genuine one comes in a regular orange and white cardboard box with the Mi logo & QR code and lasts for 2 days with moderate use. I bought it because I couldn't find the genuine one and I regretted it. I put back my previous (genuine, replaced) one that I had been using for 2 years and it works better than this one.

I bought it 4 months ago. Today I decided to install it. As soon as I opened the packaging, it smelled like glue. I installed it and it simply wouldn't charge.

I bought it to replace the original one that, after two years of heavy use, I had to charge twice a day. It doesn't last as long as the original (but I think batteries of the same quality as the original ones are not available in the market, even if they are from the same companies), but it still lasts a decent amount (I can comfortably get through a day now).

Because before I order anything, I always check the reviews, that's why I decided to write my own. The battery is exactly the same as the one that comes with the phone, no power loss, fits perfectly, and the delivery through the skroutz basket is immediate.

I don't know if it's the new screen I installed, but my battery barely lasts a day, while before, two years ago when the phone was new, it would last for two days with usage. Generally, the battery drains quickly, and when I plug it in, it only goes up by 4-5% in a few seconds, which shouldn't happen with a new battery.

Edit 01/12/20:
I probably got a defective one, and now it's too late to change it... Anyway, after a month, the battery doesn't hold at all, and when the phone is not in use, it drops from 100% to 60% in 6 hours with power saving ON (now I have it permanently on because otherwise the phone won't even last half a day)