The collar does not stretch itself, please make sure leave only 2 fingers between collar and dog neck, a properly fitting collar and harness won't leave any room for your dog to chew. The collar is not for tie out. Never leave your dog unattended with a collar on. Made of quality neoprene webbing and polyester ribbon sewn on top, all buckles are made from plastic, the metal d ring is black coated to add durability