The PetSafe® Spray Refill cartridges are easy to replace with no mess. Simply remove the empty cartridge and replace with the new one. The citronella scent is harmless to your dog and is meant to act as a distraction to help stop nuisance barking. The Spray Refill cartridge is 100% recyclable and safe for you and your dog! Key Features: •Compatible Collars – The Spray Refill - Citronella is for use with the PetSafe® Spray Bark and Training collars; it is NOT compatible with the Elite Big Dog and Little Dog Spray Bark Collars or Elite Big Dog and Little Dog Spray Trainers. •Easy-to-Replace – The refill cartridges are easy to replace; simply remove the empty cartridge and replace with the new refill cartridge. •100% Recyclable – The disposable Spray Refill cartridges are 100% recyclable. Features: •Compatible with PetSafe® spray Bark Control Collar (PBC17-16369) or spray Remote Trainer (PDT17-16396). System Includes: 3 Citronella Refill Cartridges. Each cartriges delivers between 35-40 sprays.