20 the pressure foot 22 is disposed to abut a second end of the cartridge piston 10 a second thread 24 extends from a second end of the piston rod 20 in the illustrated embodiment the second thread 24 comprises a series of part threads rather than a complete thread the illustrated embodiment is easier to manufacture and helps to reduce the overall force required for a user to actuate the device when dispensing the medicinal product the first thread 19 and the second thread 24 are oppositely disposed the second end of the piston rod 20 is provided with a receiving recess 26 a drive sleeve 30 extends about the piston rod 20 the drive sleeve 30 is generally cylindrical the drive sleeve 30 is provided at a first end with a first radially extending flange 32 a second radially extending flange 34 is provided spaced a distance along the drive sleeve 30 from the first flange 32 an intermediate thread 36 is provided on an outer part of the drive sleeve 30 extending between the first flange 32 and the second flange 34 a helical groove thread 38 extends along the internal surface of the drive sleeve 30 the second thread 24 of the piston rod 20 is adapted to work within the helical groove 38 a first end of the first flange 32 is adapted to conform to a second side of the insert 16 a nut 40 is located between the drive sleeve 30 and the main housing 2 disposed between the first flange 32.