The fluid infusion system is disclosed that includes a pump housing that has a reservoir cavity and is designed to be pocketable. The reservoir cavity has a rim and helical coupling features formed on an interior face of the reservoir cavity. The fluid infusion system further has a reservoir that is removable from the reservoir cavity and the reservoir also has an open end. A removable cap coupled to the pump housing is also included in the fluid infusion system. The cap has corresponding coupling features, an exterior surface and a tab. The corresponding coupling features are defined to couple the cap to the pump housing while the tab is defined as a ridge that extends away from the exterior surface. The tab further has a port to accommodate fluid flow from the reservoir where the port defines an axis of rotation such that torque applied to the tab about the axis of rotation disengages the coupling between the cap and the pump housing. Further included in the infusion system is a guard that is removably coupled to the pump housing. The guard has a slot defined to immobilize rotation of the tab about the axis of rotation.