Sterling Silver 925.
Tarnish is a fact of life and a natural characteristic of silver. The jewellery will need cleaning ever so often with the polishing pad from your Ousiai package to restore the original brilliance of the surface.
For a more thorough clean you can also soak your silver jewellery in 1/2 cup white vinegar mixed with 2 tablespoons of baking soda for two to three hours. Rinse under cold water, and dry thoroughly to bring back that luster and shine.