Medicament delivery device and medicament delivery assembly

A cap assembly for a medicament delivery device, the medicament delivery device having a proximal end and a distal end and defining an axis extending proximodistally, the cap assembly comprising an outer cap and a needle cap,

• wherein the needle cap has a fastening structure for the needle cap to be fastened to a retaining structure of the medicament delivery device, the fastening structure cooperating with the retaining structure so that a removal of the needle cap from the retaining structure requires a rotation of the needle cap relative to the retaining structure in an opening direction,
• wherein the outer cap has a cap wall extending from a proximal end towards distally, around the axis, coaxially with the needle cap, with a distal rim, a plurality of cut-outs extending from the distal rim towards proximally, and therebetween an arm arrangement with at least one arm section,
• wherein the at least one arm section is capable of being resiliently flexed radially-inwardly and has, on an inner side, an outer coupling structure,
• wherein the cap assembly further comprises an inner coupling structure rotationally coupled to the needle cap,
• wherein the outer cap is rotationally de-coupled from the needle cap when the arm arrangement is in an initial, un-flexed state,
• wherein a rotational coupling between the outer cap and the needle cap requires the arm section or at least one of the arm sections to be flexed inwardly for the outer coupling structure to engage with the inner coupling structure, and
• wherein removal of the needle cap from the retaining structure requires the outer cap to be rotated in the opening direction, with the arm section or at least one of the arm sections flexed inwardly.