Purchased for €2.08 without shipping. At this price, I can say it's worth the money. Initially, it was tested on a rusty surface (metal) and applied with a brush, a method not recommended by the manufacturer and did not yield significant results. Then, I tried putting various accessories such as screws, wheels, nuts, and the gear in the photo in a container with a sufficient amount to cover them completely for a total of half an hour, shaking the mixture every 5 minutes and lightly scraping with a wooden stick where there was heavy rust. The results were very good! I cleaned the accessories well afterwards and lightly rubbed them with a Scotch-Brite type wire (1-2 minutes per accessory)! Very satisfied with the outcome, but you should consider what is ultimately worth derusting. The product weakens as you use it (logical), so in my opinion, it's only worth using it on accessories that are not easily and cheaply found in the market (e.g. I wouldn't use it on screws, wheels, and nuts M4, M5, M6, etc.).

WARNING: It is a caustic chemical with a very strong odor! I always use it with goggles, gloves, and a mask, and I recommend the same to you!