PACKAGE CONTENTS: Package contains HW241 72LED microscope ring light and charging cable. Reference dimensions: inner diameter 45mm (1.77 in), outer diameter 75mm (2.95 in), silver finish for lab and bench setups. ADJUSTABLE BRIGHTNESS: Smooth linear dimming from 20% to 100% via a tactile knob gives precise light control for both coarse inspection and detailed work using microscopes. UNIFORM ILLUMINATION FOR REFLECTIVE SURFACES: Ring layout casts even light that reduces shadows on reflective samples such as metals and jewelry, aiding defect detection and close-up photography. WIDE COMPATIBILITY: Designed to work with most monocular and stereo microscopes, this compact ring light integrates easily into scientific research, industry and classroom environments. LONG LIFESPAN & SAFETY: LED lifespan exceeds 100,000 hours with stable operation and low heat generation for prolonged use. PLEASE CHECK THE PRODUCT SIZE CHART INSTEAD OF AMAZON'S SIZE CHART.