Eli5, why do Mason jar lids typically come in 2 parts, threads and seal, as opposed to nearly every other commonly used household container?

Question

Eli5, why do Mason jar lids typically come in 2 parts, threads and seal, as opposed to nearly every other commonly used household container?

In: 7899

Answer 1

Before WWII they were one part reusable rings saved metal. You can still purchase one piece lids.