The revolutionary new way to add Fluoro-Lite fluorescent dyes into vehicle air conditioning and refrigeration systems -- without the use of additional refrigerant. Just one connection, then turn the handle to inject the dye, no complicated hookups! When the cartridge is empty, just throw it away. A new one connects in seconds and is ready to go. Ideal for preventative and programmed maintenance. The dye remains safely in the system for future inspections, too.