“PEI” is the abbreviation for Porcelain Enamel Institute. A PEI Rating is given to a tile product based the hardness of its glaze. This hardness is determined by the manufacturer using a standardized test. The results of this test will determine the proper usage of a product.Click to see full answer. Considering this, what is the highest PEI rating for tile?The PEI rating indicates the tile hardness, and these ratings are valuable to help in tile choices for different projects. The scale ranges from one to five, with five being the strongest and most durable.Also Know, what is the strongest type of tile? Porcelain ceramic tile People also ask, what are the grades of porcelain tile? Porcelain tile is graded on a similar scale. The Porcelain Enamel Institute (PEI) has established ratings ranging from 0 to 5, whereas 0 represents the softest tiles suitable for wall applications and 5 represents the hardest tiles suitable for heavy foot traffic.What is grade 5 porcelain tile?The toughest porcelain tile available on the market, Grade 5 tiles are used in areas that receive very high foot traffic and are prone to a lot of wear and tear. They are popular for installation in schools, hospitals, grocery stores, and industrial buildings. Grade 5 tiles can hold up to harsh chemicals as well.