Thomas Sabo Ring from the Sterling Silver Collection. The secret of the cosmos is reflected in the never-ending universe of colours of the dazzling sapphire-blue THE SECRET OF COSMO ring: the sensual, hammered look of the blue synthetic corundum in the Thomas Sabo signature cut and the feminine cushion shape make this ring crafted from 925 Sterling silver reflect light like sparkling stars. With a width of 1.3cm and a ring size of O.