Medical devices, such as endoprostheses, and methods of making the devices are disclosed. The medical device can include a stent body and a cover including a deposited metallic film. The medical device can be delivered using a delivery device along a tortuous body passage to a treatment site without damaging the medical device, delivery device, or the body passage. In some cases, the stent body is a flexible helical stent body, which may be threaded through one or more fenestrations of the cover. The cover may include longitudinally extending slits or seams, which help the cover to pass through small radii passages without buckling.