Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Didn't perform as expected

My sick dog was chewing his fur and this product did nothing to help him. In fact, the abrasive edge was used by the dog to rub itself causes even more bald spots. For some reason, the large dog version wasn't big enough because it was able to still chew on fur and my dog is only a 50 pound german shepard mix. Not sure if this product works as intended, it certainly did not for my dogs. Only good point is the velco, which does not break like the cheap plastic tabs on cheaply made E-collars @ Petco.