I've had them for 1 month. The build quality is average, but for the price, they are just right. If you want to buy them to use with dumbbells, NO, don't do it because they are too thick; personally, I use them as extra weight in a dipping belt, since I perform several calisthenics exercises. If you also want them as extra weight, don't buy them either because they are thick, although their price is tempting. Lastly, they slip a lot; you can't even hold them, but personally, they work for me now for the use I give them. Later, I will sell them since I will get twenty-kilogram weights. I will update you here or send me an email if you are interested. I might even give them away for free or at a ridiculous price.

Quite good weight, as shown in the photo. It slides a little.
Personally, for abdominal use, I would get one with handles because this one slides a bit (and it also has some kind of coating on top that seems to "grease" the hands but I'm not sure).
Otherwise, excellent for its price!

For its price, it's fine. It's not made of iron, so obviously you shouldn't throw them down. Their downside is that they have a large diameter and are not the best for dumbbells.