Modified Glow Penlight Live, Set of 2, UO Concert Light, Cyalume, LED High Brightness, Support Light, Ultra-Lightweight, Batteries Included (Yellow) I opened and tested only one to make sure it works. Please note that this is not a flashing type. It is not a button switch type; it turns on and off by twisting the battery cap. There is no guarantee of operation in the buyer's environment. Thank you for your understanding, and we look forward to your purchase.