GGG40 and GGG50 are grades of ductile iron, differentiated primarily by their tensile strength and microstructure. GGG40 has a minimum tensile strength of 400 MPa, while GGG50 has a minimum tensile strength of 500 MPa. This difference in strength is due to the higher alloy content and improved mechanical properties in GGG50, making it suitable for more demanding applications. Additionally, GGG50 typically exhibits better wear resistance and ductility compared to GGG40.