Ru ware is the rarest and most celebrated of all Chinese imperial wares. It was made for the late Northern Song court for a very short time and was therefore extremely rare and precious. Simplicity and refined elegance are Ru ware's hallmarks. Its graceful shape, soft luster, and subtle color variation of the glaze interact in perfect unity. Other physical characteristics include an ash-grey body, soft greyblue glaze with a fine crackle, as well as small sesame-seed spur marks on the base.