Abstract: The injection cartridge comprises two containers (1, 2) one of which is slidably mounted in the other. An actuating rod (8) has a smooth leading portion (9) and a rear threaded portion (10) separated by a threaded intermediate portion (11). The container (1) has in its end (12) a threaded opening (13) receiving the threaded intermediate portion (11). The nozzle (5) of the container (2) has a thread (15) for receiving the thread (14). The threaded portion (10) of the rod (8) has a nut for abutting against the first container to push it towards the other container. The cartridge may be used for injecting a semi-pasty product into a protective sleeve for a joint in a telephone cable.