It is very good. On a carpet that I was going to throw away because it kept shedding this yellow powder and was slippery, it became perfect. Of course, I applied it 3 to 4 times.

It works if you follow the instructions perfectly. I glued the worn-out underlay of a 70s rug that was rubbing against sand. I will need a second package though, as it recommends two coats for greater durability. I applied it with a synthetic brush that can be cleaned with water and soap afterwards. If you make any mistakes, wipe them off before the product dries.

It seems to be doing a good job. So far (1 month later), the underlay has not produced any dust. Keep in mind that there used to be a mess before, so I am optimistic that we saved our carpet and our wallet.

The carpet has retained its elasticity, so when you roll it, you don't see the glue breaking or anything like that. For now, everything is good. Of course, I will come back in the summer when we take it out to see what it has done after a few months.

Some observations for the users, not for the product:
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The glue does not become elastic and the carpet does not become non-slip because of the glue. That is, you will not see a layer of rubber underneath or anything like that. What you will see is the underlay being saturated with glue and its structure becoming more stable so that it is no longer loose. That is exactly what it claims to do. However, it does not become non-slip with this material. Not at all! I had it spread out for 3 days to dry. It does not dry in 24 hours as they say.
For a normal living room carpet, 3x2 meters, I used exactly 3 boxes - 2 hands. What is 1 box for 5 square meters.