The jars are glass (one set specifies lead-free borosilicate glass). Lids include metal/steel, glass, and bamboo, and some designs use rubber gaskets for sealing.
Capacities span roughly from 32 fl oz up to 138 oz. Common sizes shown include 32 oz, 33.75 oz, 50.75 oz, 54 oz, 75 oz, 128 oz, and 138 oz.
Listed neck/mouth sizes include about 3.4 inches, 3.25 inches, and one multi-jar set notes 4-inch wide mouths for easier scooping.
Many jars use hermetic or airtight lids with rubber gaskets and clamp-style closures. Some use secure twist-on lids; reviewers frequently note airtight sealing that helps preserve contents.