I often vape huge multi-battery mods and consider myself lucky to leave the house without a couple of 21700 spares.
No surprises here, as the 1.
The large center hole is airflow for the coil.
Change the coils as you wish between G2 compatible replacement coils offered in 0.
There are two spring loaded contacts inside to make contact with the coil once the pod is inserted.
Caliburn G2 can be activated by auto-draw or button.