Abstract: This relates to the formation of wide mouth bottles and jars for receiving a hot fill product where the jars and bottles are formed of a suitable polyester such as PET. The bottle or jar is initially formed as part of an intermediate article including an upper adapter portion which is reusable so that substantially all of the resultant bottle and jar, particularly the neck finish thereof is biaxially oriented. The intermediate article is formed from a preform which is blow molded within a conventional type of blow mold. In the reheating of the preform, that portion of the preform which becomes the neck finish of the bottle or jar is heated to a higher temperature than the remainder of the preform and to a temperature wherein thermal crystallization in addition to strain crystallization occurs. This results in the neck finish having a higher density than other portions of the bottle or jar and being more resistant to shrinkage during hot filling.