The Ceramic Scraper is a tool designed for removing flash and other imperfections in plastic models by scraping away unwanted plastic with the dull Zirconia ZrO2 blade. 

Just run the edge of the blade along the plastic and watch as the plastic shaves off easily, leaving an even and clean finish. 

Watch a demonstration on how to use this product here : https://www.youtube.com/watch?v=kVs_FJr1j4k