MULTI-DOG SYSTEM: This kit includes 2 collars, 100 boundary flags, and 1000 ft of wire to help get you started. EASY TO INSTALL: Containment kit includes everything needed to cover 1 1/3 acres of land for one dog; can be expanded to cover 100 acres with more wire and flags (sdf-wf) WATERPROOF AND RECHARGEABLE COLLAR: Included collar features lithium-ion batteries with 2-hour quick charge and one to two month battery life: waterproof and submersible to 25 ft. With dryer technology UNLIMITED DOGS: Contain an unlimited number of dogs with additional collars (SDF-CR); fits dogs 10 lb. and up TONE, VIBRATE, AND STIM: Collar gives Tone (beep) and vibration (Buzz) warning before moving to one of seven static stimulation levels (you choose the best level for your dog)