Lifesystems Glow Markers contain photo-luminescent crystals that absorb light & then glow for up to 12 hours. The crystals are contained in a tough acrylic case is waterproof to 30 metres & has a locking wire loop for easy attachment. To get the crystals glowing simply expose them to a bright light, a torch for example, for about 5 minutes. They will absorb the light then give off a glow that is easily seen in the dark. Attach it to guy lines to avoid tripping, bits of kit to avoid loss, or even dogs for dark walkies. The uses are endless & the crystals have a rechargeable life of up to 10 years. Please note that the crystals all emit the same yelow/green glow irrespective of the case colour. Photo-luminescent technology Supplied with cable ring attachment One 5 minute charge lasts up to 12 hours Crystals have a 10 year rechargeable life