The two silver parts on the back are reflective to ensure the safety of dogs walking at night. Material: Aluminum Bar SBR Foam Function: If a pet with blurred vision walks with an obstacle in front of it, the anti-collision ring will feed back to the pet when encountering an obstacle, thereby avoiding accidental injury to the pet. Collar and bust size can be adjusted. Product Size: S=circle diameter 22CM (for 4-10KG) collar 28-40CM, bust 32-45CM M=circle diameter 33CM (suitable for 13-20KG) collar 32-45CM, bust 36-50CM Protect Your Pet: Designed especially for blind sick eyes pets, helps pets with poor vision due to SARDS, glaucoma, cataracts, retinal diseases, trauma, and diabetes.prevent them from colliding wall or other accidents and protect them.does not affect daily activities, such as sleep, eating and so on. Adjustable Ring: The size of the collar can be adjusted. Build Confidence: When your pets start to adapt to this anti-collision device, they will learn to trust this device, and our equipment will help your pet rebuild confidence in life. Because this device will guide them to avoid hitting hard objects and protect themselves.