ST stands for step cut nanosital like Asscher and Emerald shapes. Step cutting arranges broad facets in parallel rows resembling stair steps. This creates a hall of mirrors to intensely reflect light. To avoid visible inclusions, step cut nanosital demands immaculate clarity. The Asscher shape conceals flaws more readily than Emerald cuts. The resulting contrast of light and dark facets produces a sophisticated, Art Deco style. Nanosital's flawless transparency perfectly complements the calculated step cut.