A sub-assembly for a medicament delivery device configured to expel medicament from a medicament container. The sub-assembly comprises a housing and a medicament container carrier. The medicament container carrier comprises a carrier wall having an open proximal end, at least one slot extending from the open proximal end in a distal direction, and at least a first leg portion and a second leg portion radially separated by the slot at least at the open proximal end such that the first and second leg portions are radially movable relative to each other. The sub-assembly further comprising a tubularly shaped retaining element and a cap comprising a protrusion extending distally into the proximal end of the housing, wherein the retaining element comprises a first engaging structure releasably engageable with an associated second engaging structure of the distally extending protrusion, such that the retaining element is releasably engaged to the distally extending protrusion.