AmScope LED-64-ZK Microscope Ring Light with Adapter 64 bright white LED bulbs; 100,000 hours lifetime Intense and focused shadow-free illumination; variable intensity control Inside diameter of ring light: 2-1/2" (64mm); outside diameter of ring light: 4 (100mm) Power input: 110-240V, 50-60HZ, auto switching Fits up to 2-1/2" (64mm) mount rings