Abstract: In a cartridge comprised of a base member including a hub for receiving a wound web and a shell cover to generally enclose the winding surface of the hub, the shell cover has been modified to prevent unintentional disengagement of the shell from the base. The base member and shell each carry a portion of a locking mechanism which enables them to be releasably locked together in a hub enclosing relationship. The locking mechanism normally requires a separate tool to disengage it when separation of the base and shell is desired. This invention concerns modification of the cartridge and shell which prevents unintentional disengagement of the base and shell due to kinetic shocks, such as dropping on a hard surface.