The two silver parts on the back are reflective to enhance visibility and ensure the safety of dogs during nighttime walks. Material: Aluminum Bar SBR Foam Function: Helps pets with limited vision detect obstacles by providing feedback upon contact, reducing the risk of accidental injury. The collar and chest straps are adjustable for a secure fit. Product Size: S: Circle diameter 22CM (for 4-10KG), collar 28-40CM, chest 32-45CM M: Circle diameter 33CM (for 13-20KG), collar 32-45CM, chest 36-50CM Protect Your Pet: Designed for pets with visual impairments, supports those affected by conditions such as SARDS, glaucoma, cataracts, retinal diseases, trauma, or diabetes. Helps reduce collisions with walls and other objects while allowing normal daily activities like sleeping and eating. Adjustable Design: Collar size can be customized for comfort and proper fit. Build Confidence: As pets become accustomed to the anti-collision ring, they may gain confidence in their movements. The device helps guide them around obstacles, promoting independence and self-protection.