Monocular Max 300x Zoom C-mount Glass Lens Adapter F/Industry Digital Microscope Camera Objective Objective Magnification Power by 0.7 - 4.5X(about 10 - 300X on the 21 inch display) 1.0X C-mount adapter Working distance: 100mm-115mm Monocular 300X Industry Zoom C-mount Lens focusing mechanismFocusing handwheel tightness is adjustablefocusing range 15mm & 40mm