Absolutely convincing product. Helps against all rust spots on the gelcoat. Spray on, wait 15 minutes, rinse off. Possibly. to repeat. The best results are achieved at lower temperatures (approx. 15 degrees), i.e. difficult to use in the Mediterranean region in summer. The black running noses also disappear.
Very expensive and ineffective. I tried to remove rust discoloration from my stone tiles on the terrace - which was caused by iron-containing lawn fertilizer. The drug had no effect.