Radiator Dosing and Testing Apparatus, comprising: a target arrangement valve body configured to be installed within an access inlet of a radiator, and a product dispensing device; said target arrangement valve body defines a target arrangement passage, and comprises a normally-closed two-way valve member within said target arrangement passage; said product dispensing device comprises an outlet that defines an outlet passage, and a compartment arranged in communication with said outlet, said outlet is provided with an openable closure means, said target arrangement valve body presents a female-threaded target arrangement engagement formation, said product dispensing device presents a male-threaded outlet engagement formation, and said male-threaded outlet engagement formation of said product dispensing device and said female-threaded target arrangement engagement formation of said target arrangement valve body are configured to mechanically engage through the rotation of said male-threaded outlet engagement formation into said female-threaded target arrangement engagement formation; said male-threaded outlet engagement formation is rotatable into said female-threaded target arrangement engagement formation into a fully engaged condition in which said target arrangement passage and said outlet passage are in sealed communication; and said target arrangement valve body and said product dispensing device are cooperatively configured such that: rotation of said male-threaded outlet engagement formation into said female-threaded target arrangement engagement formation towards said fully engaged condition opens said normally-closed two-way valve member within said target arrangement passage; characterized in that said compartment is flexible and is presented to receive a manually applied compressive force thereto. a target arrangement valve body configured to be installed within an access inlet of a radiator, and a product dispensing device; said target arrangement valve body defines a target arrangement passage, and comprises a normally-closed two-way valve member within said target arrangement passage; said product dispensing device comprises an outlet that defines an outlet passage, and a compartment arranged in communication with said outlet, said outlet is provided with an openable closure means, said target arrangement valve body presents a female-threaded target arrangement engagement formation, said product dispensing device presents a male-threaded outlet engagement formation, and said male-threaded outlet engagement formation of said product dispensing device and said female-threaded target arrangement engagement formation of said target arrangement valve body are configured to mechanically engage through the rotation of said male-threaded outlet engagement formation into said female-threaded target arrangement engagement formation; said male-threaded outlet engagement formation is rotatable into said female-threaded target arrangement engagement formation into a fully engaged condition in which said target arrangement passage and said outlet passage are in sealed communication; and said target arrangement valve body and said product dispensing device are cooperatively configured such that: rotation of said male-threaded outlet engagement formation into said female-threaded target arrangement engagement formation towards said fully engaged condition opens said normally-closed two-way valve member within said target arrangement passage; characterized in that said compartment is flexible and is presented to receive a manually applied compressive force thereto. rotation of said male-threaded outlet engagement formation into said female-threaded target arrangement engagement formation towards said fully engaged condition opens said normally-closed two-way valve member within said target arrangement passage; characterized in that said compartment is flexible and is presented to receive a manually applied compressive force thereto.