These are a pair of brand new super widefield high-eyepoint 30mm WH10X/20MM microscope eyepieces. They are Achromatic (International DIN/JIS) standard size with outside diameter of approx. 30 mm. They fit most common size stereo microscopes. Give your microscope a boost with greater power & clarity at a fraction of cost. Features & Specifications : 10X Magnification Power 20 mm Super Wide Field of View 30 mm Mounting Size (in diameter) High Eye-point Design.