2.5" overall. Water resistant. Impact resistant. Clip. Rechargeable. Modes: Turbo (1300-600-300 lumens, 1.5+2.5+73m runtime); High (600-300-60 lumens, 7+72+16m runtime); Medium (60 lumens, 8h runtime); Low (12 lumens, 35h runtime); Moonlight (0.5 lumens, 30 day runtime). Requires (1) Lithium battery (included). Aluminum construction.