Product Features LightShape circular green light marker for providing illumination for up to 4 hours Measures 3a ^2 in diameter and has an adhesive back for attaching to surfaces Chemiluminescent substance is non-toxic and plastic body is phthalate free for safety Four-year shelf life from date of manufacture for a maintenance-free alternative to other lighting Can be used for many applications, including evacuation procedures, medical triage, trail marking, and more