Scrapers are used for shaping, smoothing and trimming pottery shapes. The steel scrapers (S) are made from thin flexible spring stainless stee. The S11S and S12 is slightly heavier gauge steel, making them somewhat stiffer. The aluminum scrapers (SA) are made from a high-strength aircraft alloy that is much more rigid. The rigid scrapers can also be used as a squeegee to remove excess water from pottery shapes. The S4, in the picture, is the third scraper of the four.