Gerber Cortex Compact Cree XPG-R5 LED Flashlight 31-002308 30-000822. With regard to originality and thoughtfulness, this Gerber Cortex Compact LED flashlight model 31-002308 30-000822 gets a 10 out of 10. This flashlight uses an intense cree XPG-R5 L.E.D. lamp as its light source. What is really cool about it is that the light can operate off or a single AA battery or a single CR123 battery. Talk about versatility! The light has low and high output options for shining serious light when you need it and conserving battery life the rest of the time. When the Gerber Cortex is operating with a single CR123 battery the performance is as follows: high mode output - 125 lumens, high mode runtime - 1.5 hours, low mode output - 25 lumens, low mode runtime - 9 hours. When the Gerber Coretex is operating with a single AA battery the performance is as follows: high mode output - 60 lumens, high mode runtime - 1.25 hours, low mode output - 12 lumens, low mode runtime - 6 hours.