“Mason” is still the common term for the jar but they are also referred to as Ball jars, fruit jars or canning jars.  Today’s common brand names are Ball, Kerr and Bernardin (Canada), all now made by Jarden.

The jars have a standard continuous thread in two sizes: regular mouth and wide-mouth.  This is the common definition of mason jars, however, any screw-neck jar can be considered a “mason jar”.  In fact, you can find  jars that have “Mason” embossed on them that are neither the standard sizes nor have a screw thread.  So when reCAP states that the caps fit most mason jars, it’s with these variations in mind. 

Jars come in a variety of volumes for both mouth sizes, as small as 4 ounces or as large as a gallon.

Illustration by Minnetrista, “ Jars From a Century of Progress”