What characteristic of the training collar is important for proper application?

The characteristic that is crucial for the proper application of a training collar is that it should fit snugly and comfortably. A collar that fits properly ensures that it provides effective training without causing harm or discomfort to the dog. A snug fit helps in administering cues or corrections effectively, while also preventing the collar from slipping off or becoming too tight, which can cause injury. This balance is essential for maintaining safety and the dog's well-being during training sessions. Proper fit also allows the dog to express normal behaviors without restrictions that could arise from an ill-fitting collar.