2.63" overall. Clip. Nichia 219C LED with lifespan up to 50,000 hours. Glow in the dark diffuser and front O-ring. Aluminum alloy orange peel reflector. Anti-reflective lens coating. Modes: High (170 lumens, 75m runtime), Medium (48 lumens, 8h runtime), Low (1.5 lumens, 65h runtime). Requires (1) AAA battery (not included). Copper construction. Bulk packed.