Ledlenser K4R Small light, big power. The K4R is a rechargeable keychain light with up to 120 lumens of light output, making itsignificantly brighter than most smartphone flashlight functions. No more messing with annoying cables as the light can be conveniently charged using the integrated fold-out USB-A interface. With its compacted brushed aluminum housing, the K4R combines a high-quality look and feel, making it an elegant and practical accessory for your key ring.