The PetSafe Remote Spray Trainer Add-A-Dog Collar PAC00-13736 lets you train 2 dogs using 1 remote.  You must already have the transmitter for this collar to work. The transmitter is not included. The extra collar comes with 2 spray refills-unscented and citronella.  Each cartridge has about 35 sprays.  

NOTE:  This collar will only work with PetSafe Remote Spray Collar mode PDT00-16395. 

  Features

• Range up to 300 yards
• Rechargeable collar
• 3 Training options-Tone, Vibrate, Spray (transmitter needed-not included)
• Adjustable collar for neck sizes up to 27"
• QuickFit buckle for a perfect fit and quick release every time
• Water resistant receiver collar 
• Good/low battery indicator light 
• Expect about 35 sprays per refill on average
• Safe for all dog breeds of any size
• One Year Warranty from PetSafe (important when buying any sort of electronics) 

 Box Includes

• Training Collar
• USB Charging Cable
• 1 Unscented Refill Cartridge (PAC00-16646)
• 1 Citronella Refill Cartridge  (PAC00-16371)
• One Year PetSafe Warranty