A cylindrical rotator for a medicament injection device is provided. The cylindrical rotator comprises a needle shield and a plunger. Said cylindrical rotator is arranged with mechanical members on its surface that are configured to co-operate with mechanical members arranged on the needle shield, so as to cause a relative turning action therebetween. Said plunger is arranged with a protrusion for being held by a stop ledge, the protrusion being configured, by said turning action, to move past the stop ledge, whereby the plunger is free to act on a content of the medicament injection device and thus to inject a dose of medicament.
