Our shoe stain and yellowing gel contains penetrant, whitening enzyme. It can not hurt the shoes, remove the yellow, make the shoes clean and bright. Its use method is very simple: 1. Wipe the yellow part of the shoe and put tape on the edge of the yellow place. 2. Apply the product to the yellow part of the shoe. 3. Leave for 6-8 hours after applying. 4. Scrub the stain with clean water and wipe it dry. And can be strong decontamination, chemical removal of yellow dirt, fundamentally restore its true color.