HD24 Pre Grind – most aggressive gelled acid This product is used for etching concrete: When a very aggressive opening is needed. HD24 Pre Grind will give you approximately 100-80 sand paper grit opening As a “Pre Grind” for polished concrete floors. When you need to remove contaminants such as grease and oil, mold and mildew, etc. HD24 Pre Grind is designed to be aggressive on top laitance MAKE YOUR 1ST CUT COUNT!! EXTEND THE LIFE OF YOUR DIAMONDS!!