Muffin's Halo is a halter for vision-impaired/blind dogs. There is a "halo" or half-circle covered wire that extends from the halter to beyond the snout of the dog. When approaching an obstacle the halo prevents the dog from walking into it. It is adjustable, washable and it works! This MH was used twice by my blind labradoodle (40 lbs). It was snug on him (size large) but that's necessary so it doesn't move around. The size chart is on Amazon under Pet Supplies & Muffin's Halo- click on any of the Muffin's Halo items.