The anti-collision ring can adjust the height back and forth, up and down. S = ring diameter 22CM (suitable for 4-10KG) collar circumference 28-40CM, bust circumference 32-45CM M = ring diameter 33CM (applicable to 13-20KG) collar circumference 32-45CM, bust circumference 36-50CM High-Quality Materials: Blind Dog Harness is made of aluminum, SBR, foam material, odorless, can be used repeatedly and durable for long time use. EASY TO PUT ON - This halo for blind dog comes attached to a vest harness so your pet can wear it easily. The Blind Dog Harness Guiding Device is adjustable and secured by touch fasteners to ensure that your dog is comfortable as they learn to adapt to their poor vision. The pet ring is adjustable according to your pet's size, easy to wear.Suitable for small or medium cat and dog, allows your blind pets to quickly and safely become familiar with their surroundings. Lightweight, Blind pets collision ring does not affect daily activities, such as sleep, eating and so on.Anti-collision ring is made of Aluminum, SBR, foam material, odorless, can be used repeatedly and durable for long time use. Protect your Pet: Blind Dog Halo Collar Helps blind pet to stay safe and move freely, prevents it being hit in the street. And helps to prevent painful bumps from running into walls, furniture, and other obstacles.