Reflector optics deliver up to 400% more lighting range than traditional penlights. Easily attaches/detaches to just about anything with convenient pocket clip or key ring. Up to 96 hours run time. Includes neck lanyard. O ring sealed for water- resistance The world's smallest, brightest, one-ounce, machined aluminum, one LED flashlight! The Key-Mate runs longer and stays brighter, Powered by 4 LR44 high alkaline button cells (included). 100,000 hour lifetime high-intensity LED with reflector optics.