Abstract: A closure cap is disclosed for sealing containers and particularly for sealing thin-walled vacuum formed containers with threaded rims. The closure cap is a composite closure having a molded plastic ring for engaging the container and for mounting a disc-like metal cover. The metal cover includes a vacuum indicating disc particularly adapted for providing a positive indication for relatively low vacuums and the closure cap is adapted for being sealed onto the container with a combination of press-on and screwing action to provide for high speed vacuum sealing. The vacuum indicating action of the vacuum button is improved by providing a channel in the plastic ring at the edge of the metal cover for stablizing the button operation at the desired low vacuum levels.