After trying every training collar on the market, I can tell you PatPet is the only one that works for me. I have a very stubborn Great Pyranees who never stops barking and refuses to come in the house unless he’s wearing this collar. Just the threat of shock brings him running to me. I went to charge this collar until I realized it would not fit my dogs neck. It extends to 27” per company page on Amazon and fits small, medium and large dogs up to 120 lbs. Has noise, vibration and shock. Patpet is the only collar where the shock mode has had an effect. Their collars are very strong and after using the shock mode once, I never had to use it again. I love PatPet. Had to buy multiple collars because my Golden keeps chewing it off of his neck when they play. FREE M-L Dog Harness with purchase.