Small holes of different diameters are provided in the optical system to meet different light transmission requirements. 2. The compact and practical structure makes the diaphragm work more stable, light in weight and easy to operate. 3Made with high-quality precision workmanship, high quality, long service life, high strength and good durability. The enlargement and reduction range of the 4 inner holes is 1.534mm, which can meet your needs and adapt to various optical instruments, cameras, etc. 5. The material is made of aluminum alloy, which is not easy to rust, has good hardness, is corrosion-resistant, has low density, is reliable and durable. Product type: Iris aperture Material: Aluminum alloy Color: As shown in the picture Model: SK34 Outer diameter size: about 49 mm/1.93 inches Inner hole size: about 1.5-34 mm/0.06- 1.34 inches Thickness: about 5.6 mm/0.22 inches Application: Laser cameras and other optical instruments Packing list: 1 x Aperture Notes: 1. Please allow 12 inches of error due to manual measurement. Thank you for your understanding. 2. Monitor calibration is different, and the color of the product shown in the photo may be slightly different from the actual product. Please refer to the genuine product. 3. Please be aware of the sharp edge of the blade, be safe when using it and do not put your hands on the blade.