This is a 100X DIN-standard objective lens for compound microscopes. It features achromatic color-correction, and plan field-correction. It has a high numerical aperture of 1.25, requiring the use of immersion oil. Features Specifications: Magnification: 100X NA: 1.25 Optical Working Distance: 0.234mm Thread: RMS Mechanical Tube Length: 160mm Cover Glass Thickness:0.17mm Color Correction: achromatic Field Correction: plan Immersion Medium: oil Nosecone: spring