An apparatus for injecting an additive in a pressurized air conditioning or refrigeration system having a service valve includes a cartridge with a piston, an adapter configured to be connected to the service valve, and a bending unit interposed between the adapter and the cartridge. The bending unit includes a flexible capillary tube having a first end fitting adapted to be connected to the cartridge. The flexible capillary tube has a second end fitting adapted to be connected to the adapter. The flexible capillary tube is adapted to be bent at least at 90° without kinking.