Abstract: An apparatus for fitting heat-sealed containers comprises a conveyor for displacing a succession of the containers in a normal direction of travel through a station and for arresting each of the containers momentarily in the station, a supply at the station holding a stack of caps, a grab for taking a cap off the stack and positioning it atop the container arrested in the station and a welding tool for tack welding the cap to the container in the station as the cap is being positioned on the container and while it is still held by the grab, and a device downstream of the station for heat shrinking the caps on the bottles. The welding tool and grab are practically the same device and work very closely together. Thus there is no time during which the cap is not being positively held. Before the grab releases it, it is tack-welded to the bottle.