Durable to use: The aluminum alloy shell is precision machined.Achromatic lens: This 40X achromatic objective is designed for biological microscope.Good performance: unwanted reflections can be eliminated and contrast can be increased.Clear image: It provides high quality observation without additional chromatic aberration.Easy to use: Lens length is 37.8mm.Specifications:Item Type: Achromatic Objectives Material: Aluminum Alloy + Optical Lens Color: As Pictures Show Magnification: 40xTube length: 160mm/6.3inch Conjugate distance: 185Window cover thickness: 0.17mm Lens Length: 37.8mmMounting Size:20mm RMS Standard Thread)Item Size: 555cm/2.02.02.0inch Package Weight: Approx.62gPackage List:1 Achromatic Lens Note: The data are all manual measurement,please allow 1-3cm error,due to the light and display difference,there will be some color difference,depending on the physical item received.