Abstract: Dispenser, comprising a reservoir (10) containing fluid product, a head (20) provided with an opening (21), a piston (50) for dispensing at least one portion of the fluid product through the opening (21), the reservoir (10) being, before the dispenser is actuated, closed in sealed manner by the piston (50), the device comprising a hollow insert (60) inserted and fixed in the head (20), the insert (60) supporting a cannula (40) for piercing the piston (50) and thus connecting the container (10) to the opening (21) during actuation, wherein: said dispenser head (20) includes a proximal end portion (220) of reduced diameter the axial length of which is greater than 5 mm, advantageously greater than 6 mm, the maximum outside diameter of which is less than 8 mm, advantageously less than 7 mm, and the wall thickness of which is less than 1.1 mm, advantageously between 0.7 and 1.