LED: Cree XM-L2 Cool White (Norminal CCT 6300K). User Selectable Levels: 3 main levels (High, Medium and Low). Each main level can be programmed to one of its two sub-levels. Light Output (runtimes) - High: H1 300 Lm (0.9 hrs) or H2 184 Lm (1.7 hrs) / 116 Lm (3 hrs), Medium: M1 54 Lm (7.5 hrs) or M2 27 Lm (12 hrs) / 13 Lm (27 hrs), Low: L1 2.9 Lm (4 days) or L2 0.36 Lm (3 weeks) / 0.06 Lm (2 months) / 0.01 Lm (3 months). Beacon Strobe Mode: 4Hz Strobe at H1 / 19Hz Strobe at H1. Light output are ANSI out the front (OTF) values. Runtimes tested (and parasitic drain estimated) using Sanyo 2000mAh Eneloop AA batteries. Light output with 14500 batteries are the same except that the H1 is 535Lm for the first minute and then step down to 300Lm. Operating Voltage Range: 0.7V - 4.2V Battery: One 1.5V AA (NiMH, lithium or alkaline) or 3.7V 14500 li-ion rechargeable. Batteries are not included in the package. Parasitic Drain: Negligible (much less than the self discharging of a battery). Beam Type: 80 degree spill, 12 degree hot spot. Head Diameter: 0.86 inch (21.8 mm). Length: 3 inch (76.5 mm). Weight 1.1 oz (32 gram), 2.9 oz (80 gram) with an Eneloop AA and headband. Other Features: Battery capacity indicator (LED flashes 1-4 times, 4 short clicks to start), Low battery alert when the light is switched Off (LED flashes if the battery voltage is below 1.06V), Automatic stepping down to lower output when battery (AA and 14500) capacity is low, Built-in over-discharging protection for 14500 batteries at 2.8V cutoff, Durable electronic soft-touch switch, Proprietary heat sinking design bonds the LED board directly to the unibody aluminum casing, Sealed and potted LED driver circuitry, Tempered optical grade glass, Battery power can be disconnected by slightly unscrewing the tailcap to prevent unwanted activations or parasitic drain.