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.