This is a set of Infinity-corrected Plan Achromatic objective lenses, fitting common-size (DIN standard) compound / biological microscopes. It comes with 4X, 10X, 40X & 100X Plan Achromatic objective lenses. Features & Specifications: 4X, 10X, 40X, 100X Plan achromat objective lenses Plan flat-field corrections for a flat, well-focused field of view Achrmotaic color corrections Infinity-corrected DIN/JIS standard fittings PA4X 4X Lens NA: 0.10 Tube Length: Infinity-corrected Cover Glass Thickness: 0.17mm PA10X 10X Lens NA: 0.25 Tube Length: Infinity-corrected Cover Glass Thickness: 0.17mm PA40X 40X (Spring) Lens NA: 0.65 Tube Length: Infinity-corrected Cover Glass Thickness: 0.17mm PA100X 100X (Spring) Lens NA: 1.25 Tube Length: Infinity-corrected Cover Glass Thickness: 0.17mm Immersion Medium: Oil