The ceramic Middle rod is comprised of a porous white glazed ceramic. A plastic ring constructed from polypropene sits beneath the tank. There is certainly an o-ring created from a silica gel compound that assists seal the ceramic rod in the plastic ring at the base of your cartridge. https://johnathannjyiv.mybuzzblog.com/6284237/the-smart-trick-of-marijuana-edibles-vs-flower-that-nobody-is-discussing