Feature:1. Clearer: This lens is coated with high light transmittance, with high refractive index, and the image is brighter2. Automatic Rebound: Spring protection device, can automatically rebound when touches the cover glass during observation to protect the lens from crushing the specimen3. Brass Material: Made for brass material, fine workmanship, corrosion and fall prevention, exquisite and durable, chrome plated accuracy material for the shell4. Wide Application: The screw interface size is the international standard RMS size, which can be used by most professional biological microscopes on the market5. Basic Specifications: This lens has a magnification of 20X, common rail distance of 195mm, and parfocal distance of 45mmSpecification:Item Type: Achromatic ObjectiveModel: 20/0.40Material: BrassUse: Microscope AccessoriesInterface Size: Approx. 20.2mm / 0.80in (International Standard RMS Size)Magnification: 20XNumerical Aperture: Approx. 0.40mm / 0.02inCover Glass Applicable Thickness: Approx. 0.17mm / 0.006inMicroscope Applicable Mechanical Tube Length: Approx. 160mm / 6.30inWorking Distance: Approx. 0.55mm / 0.02inCommon Rail Distance: Approx. 195mm / 7.68inParfocal Distance: Approx. 45mm / 1.77inSpring: Yes (Automatic Rebound).Package List:1 x Achromatic Microscope Objective1 x Storage Box