Feature: 1. 1.5mm to 25mm: The aperture has an outer diameter of 55mm and an adjustable inner diameter of 1.5mm to 25mm, which provides small holes with different in the optical system to meet different light transmission requirements. 2. Simple Operation: Just use the handle to change the aperture diaphragm diameter, which is easy to operate and more directly for adjustment. 3. Reliable Materials: The aperture diaphragm is made of aluminum alloy and stainless steel, strong and sturdy, very reliable in performance. 4. Highly Stable: This diaphragm is light weight, will not add extra weight for optical systems, with high strength, rust and corrosion resistance, very stable. 5. Wide Application: This adjustable aperture diaphragm is suitable for cameras, microscopes and other machines, which can help them work better. Specification: Item Type: Iris Diaphragm Material: Alumnium alloy, stainless steel. Product Inner Hole Diameter: Approx. 1.5 ~ 25mm / 0.06 ~ 0.98in product Outer Hole Diameter: Approx. 55mm / 2.17in Product thickness: Approx. 17.5mm / 0.69in Blades: 14pcs blade. Product Thread: M42 to M42. Package List: 1 x Iris Diaphragm