Arella X50 LED (light emitting diode), USB (Universal Serial Bus) rechargeable safety tail light. Features 30-lumen light output. The fuel gauge tells you when charge is complete and when it is time to recharge. Runtime of 1 to 4 hours depending on which mode of operation you are using. Includes a durable silicone strap to fit any bar or seat post. No tools needed for installation. Modes include steady, flash, and strobe.