Special aviation aluminum alloy, high strength, impact resistance, twist and pressure. Machining process. Surface treatment: high-mesh sand blasting machine and color quality pure matte black or silver. Ultra-low chemical residues, attached to a solid! Font Handling: Font clear mission, silk screening of non-mimeo, attached to a solid! The step-up adapter rings set allows a filter/attachment with larger thread size to be used on a lens with smaller thread size. The set also can be used as a lens hood, this means that you don't need to waste extra money to a single lens hood.