This UST See-Me Strobe 2.0 personal locator light is automatically triggered when it comes in contact with water and strobes 60 times per minute.FEATURES Runs for up to 120 continuous hours Strobe rate = 60 flashes per minute (1 Hz) Visible up to 3.1 miles (5.0 km) on a dark, clear night—exceeding USCG requirement of 1 nautical mile (1.9 km) Activates when submerged in water; will not Automatically activate with rain, sea spray, or high humidity Includes PFD clip, lanyard cord, and hook-and-loop strap Easy twist on/off Ipx7 (protected against water immersion for 30 minutes at 1 meter) Size LxW: 5.5 in x 1.5 in (140 mm x 40 mm) Weight: 4 oz (113 g) with batteries BATTERIES: 2 x AA alkaline batteries (not included) For 80 years and four generations, UST Brands has provided reliable, affordable problem-solving gear for survival situations and emergency preparedness.