Uses high-quality modern led lights that glow brightly-one of the most effective high-visibility dog safety collars available. Weatherproof-good for all conditions, adjustable and comfortable for your dog. One Size Fits All: Necklace measures 50cm (Note: Length includes switch) , makes you & your dog more visible at night and in low light! flash modes: fast flash, slow flash and steady light. When the battery is sufficient, the visibility can reach 500 meters. Built-in rechargeable battery, polymer lithium battery 80 mAh 3.7V. Connect the USB cable to any common USB port for charging General waterproof function, cannot be soaked. Colour:blue Material:plastic Package Contents: 1 x Dog Collar Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.