Lightweight, water-resistant receiver can be used witdogs as small as 5 lbs. Standard lightning protection. Ideal for yard form 1/4 to 3 acres. Warning tone feature helps dogs learn the boundaries. Run-through preventer improves effectiveness. Collar receiver uses long-life, user-replaceable 6-volt battery. Includes 500' of boundary wire, wall mount transmitted with AC adapter, adjustable nylon collar with receiver, collar receiver battery, 2 sets of contact probes, installation video & test light.