37mm-40.5mm Step-Up Metal Filter Adapter Ring 37mm Lens to 40.5mm Accessory 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. Ultra-low chemical residues. Font Handling: Font clear mission, silk screening of non-mimeo, attached to a solid! High precision design, CNC Machined Made, Anodized Finish. Manufacturer Warranty,100% Satisfaction Guaranteed.