It's got a 195mm common rail distance and 45mm parfocal distance, which are standard specs that should work with most professional biological microscopes. The... I will do urgent returns and refund. Clearer: This lens is coated with high light transmittance, with high refractive index, and the image is brighter., Interface Size: Approx., 20mm / 0., 80in (International Standard RMS Size), can be used by most professional biological microscopes on the market Basic Specification: This lens has a magnification of 4X, common rail distance of 195mm/7.68, and parfocal distance of 45mm/1.77 inches. Clearer: This lens is coated with high light transmittance, with high refractive index, and the image is brighter. Interface Size: Approx. 20mm / 0.80in (International Standard RMS Size), can be used by most professional biological microscopes on the market... Automatic : Spring device, can automatically when touches the cover glass during observation to the lens from crushing the specimen. 195 Biological Microscope Plan Objective Lens 4X -100X RMS Thread 160/0 195mm Parfocal Distance Garosa 60X Achromatic Microscope Objective 60X Microscope 4X Microscope Objective Lens