These are personal vaporizers (PVs) that, for the most part, do not need or rely on internal PCB boards or other more sophisticated electronics. They generally vape at 3.7v +/- depending on the charge of the batteries used in them.
(Pictures are for illustration only) Not all mods in this section are purely mechanical. Some have wires connecting from the button. But generally anything that is not variable or ego style is in this section.