a container body made of thermoplastic materials , after being filled with a hot liquid , is then sealed by a flat closure disc adhesively contacting a peripheral lip formed around the top of the body . the bottom of the container body is formed with annular grooves to define a diaphragm which flexes inwardly with the closure disc upon cooling of the hot filled liquid to substantially dissipate the high internal vacuum which is formed in the container head space . the bottom of the container body has a reinforced pedestal base formed with stacking ledges to facilitate nesting of empty bodies for shipment and storage .