''Be safe, be seen'' also applies to our four-legged friends! The entire length of this collar glows with bright LED light. Durable webbing collar contains flexible, glowing LED/polymer tubing. With a push of the button, choose flashing mode or full-time glow. Single coin-style battery supplies up to 200 hours of light; replaceable CR2032 3V battery. Length adjusts with side-release buckle; heavy-duty D-ring attachment for a leash. Size Small fits 10 - 13 inches, size Medium fits 13 - 18 inches, size Large fits 18 - 27 inches.