AmScope EP25X23-S One 25X Microscope Eyepiece (23mm) 25X Magnification Power 23 mm Mounting Size (in diameter) It is Achromatic (International DIN/JIS) standard size with outside diameter of approx. 23 mm. It fits most common size microscopes. Give your microscope a boost with greater power & clarity at a fraction of cost. 25X Magnification Power