Features:1. Aluminum Alloy shell is precision machined, stable and durable for long time use.2. This is a 40X achromatic objective lens for biological microscope.3. It can eliminate unwanted reflections and increase contrast.4. Offers high quality observation without additional chromatic aberration, make image more clear.5. The Length of the objective lens is 37.8mm, easy to use.Specification:Item Type: Achromatic Objectives LensMaterial: Aluminum Alloy + Optical LensColor: As Pictures ShowMagnification: 40XTube Length: 160mm / 6.3inchConjugate Distance: 185 Cover-glass Thickness: 0.17mm Objective Lens Length: 37.8mmMounting Size: 20mmStandard RMS Thread)Item Size: 5 * 5 * 5cm / 2.0 * 2.0 * 2.0inchPackage Weight: Approx. 62gPackage List:1 * Achromatic Objectives Lens