Abstract: A molded extensible-collapsible container having a series of flutes, in the generic sense, in its side to permit the container when subjected to an external force to move to a collapsed position or to the extended position when preferably the yield point of the plastic is no greater than about 5% and it has an ASTM modulus of elasticity greater than about (6.895.times.10.sup.8 pascals) and less than about (2.758.times.10.sup.9 pascals) and preferably about (1.034.times.10.sup.9 pascals to 2.069.times.10.sup.9 pascals). The plastic of the blow molded container can be a blow moldable polyester of less than 5% elongation at yield with polyethylene terephthalate being most preferred.

Abstract: A deep stretch forming process for producing low distortion, biaxially oriented, heat set, hermetically sealable hollow containers of high molecular weight saturated linear polyesters comprised of deep stretching an injection molded heated contoured preform into a hollow die by means of a heated forming plunger, annealing or heat setting and then cooling the formed hollow container prior to said containers removal from said die.