Empire Flexible Silicone Skin Purple Case for Nokia Lumia 920 Specially designed Flexible Silicone Skin Purple Case for Nokia Lumia 920. Made from fully treated silicone. No mixes or blends. Chemically stable, even when impacted by heat or environmental impact. Insoluble in water, corrosion resistant, a virulent insipidity. EMPIRE is a registered trademark with the USPTO.