A fluid delivery device for delivering small quantities of fluid such as insulin to a patient, including a disposable unit having a disposable housing that has one lower part and one upper part, which together form a shell that defines an internal partial toroidal arcuate cavity. The housing fits together with a drive unit. The housing contains an arcuate cylinder for containing fluid to be delivered, a piston movably mounted in the cylinder for driving out fluid to be delivered, an adhesive support for attaching the housing and a cannula that when the housing is attached to a patient is insertable in the patients skin for delivering fluid. The drive unit is preferably removably mounted on a front of the housing opposite the adhesive support, the removable drive unit having a shape that when fitted complements the shape of the front face of the housing to form with the housing.
