It is very good for the poco x3, I have had it for over 6 months with many hours daily.
CAUTION it does not fit all mobile phones

Personally, it suited me very well. I use it for pubg and it works as it should. The negative is that it doesn't fit with any case. The construction seems to be good and the buttons are metallic.

The only issue with this is that it doesn't fit with the case, not even a slim one. Other than that, it is a nice product for the price and functionality.

It does not fit on the phone, not even without the case! It is very small! Suitable only for children's fingers, the buttons are. You cannot use all 4 buttons in any case! Also, it seems that they will break with the slightest touch. They are very fragile!

Too expensive for what it can offer. Once I tried it and once I put it back in its box!

I have had it for about three months, I bought it because I wanted something that could be easily carried, let's say in a pocket, and be easy to install and remove from the device immediately.
Relatively good construction, plastic quality, rubber bands for the back of the phone, considering that you can't ask for much more in something like this, it's not a controller. Due to the long distances I cover with public transportation and my work bus, I have used it for many hours and with rough handling, and it still feels like I bought it yesterday.
Although it is a bit risky in terms of not conflicting somewhere with the buttons (meaning to be pressed in the opposite direction of the allowed pressure), because the internal plastic stopper it has inside does not exceed 1 millimeter and it could break in a strange situation.
Easy to learn and use with all 6 fingers on the device.
Depending on the game, it is discreet and does not bother the screen too much.
It works even with tempered glass and has worked perfectly on Redmi Note 8, Redmi Note 8 Pro, and Mi 9 Pro.
With silicone cases, there was no problem with installation, with hard back cases the same. With open front cases, it depends on the case, but installation is still possible. With hard cases, it will fit, but not in all cases as it cannot "angle" well and becomes a bit annoying when pressing the buttons.

The game I have recently been playing is PUBG
Xiaomi Note 9 Pro with a silicone case and tempered glass.

Its downsides are that sometimes the springs inside make noise, but the problem is immediately solved with a little spray. I would like the springs to be a bit harder so that I can feel more that it is a trigger and not a sight, but this is purely a matter of personal preference.

For the price it is sold, I would like it to include a height adjustment for the buttons from the screen, so that depending on the thickness of the device, you can bring it closer or further away from the screen. Maybe if the buttons were based on what it lifts to use the screen (e.g. to write a message) and then lower them again.
I consider the price to be a bit high for something relatively simple, and it should not exceed 5-6 euros, although it is reliable and convenient compared to other triggers.
I will come back for any other observations...

P.S.
Dear Skroutz, I would like users to have the ability to upload some photos of the product "in action" so that potential buyers can have a better picture. Thank you.

The best thing about this analog stick..
Truly silent with comfortable pressing, stable grip on the phone.
Truly gives you the ability to use 6 fingers!!!