We recommend this dog fence if your dog is over 30 pounds and is extremely stubborn or hard to train. The Stubborn Dog Receiver has five levels of correction plus vibration in the warning area for an added deterrent and a low battery light to let you know when to replace the battery. Level five on the Stubborn Dog Receiver is approximately 25% stronger than level five on the Deluxe Ultralight Receiver and three times stronger than our Ultralight Receiver. Some breeds need the Stubborn Dog Receiver even though they may not necessarily be hard to train.  Our experience has found the Labs, Shepherds, Akitas and similar breeds often need the Stubborn Dog Receiver.  This is usually due to these breeds being less sensitive to the correction due to thick skin and/or thick fur. Receiver Size: 3 ounces - 2.25 x 1.5 x 1.25 inches.