With so many different mason jar sizes and makers, it can be difficult to know what size cap will fit your jar.
Mouth Size – The diameter of the jar opening determines the mouth size. Choose from
either regular or wide mouth sizes.
Marks a regular mouth cap Marks a wide-mouth cap
You can also determine the size of your reCAP by comparing it to the length of a standard credit card. A regular sized reCAP diameter is smaller than the length of the credit card, however a wide-mouth reCAP is just slightly larger.