100-Feet, pre-twisted Ultra-Wire by High Tech Pet Products, custom engineered and pre-twisted for use in canceling the signal field in areas where you want your dog to be allowed to cross. Twisted wire cancels the signal field and does not trigger your dog"s receiver collar. You need twisted wire to connect your boundary loop to the transmitter and to create safe zones where your dog can safely cross buried wire. Also allows you to create smaller boundaries within your yard to keep Fido away from the pool, flower beds and other off-limits areas.