I see the hybrid mods and I see the mechanical mods. What is the difference in them?
The defacto stardard interface between tanks and mods is the 510 thread interface, which is a cigalike sized interface.
There are still a few tanks that use the bigger eGo interface which is 14mm diameter, but you won't find any drippers or RBA's that use it.
A hybrid system is where the tank might be like 22 mm wide and the mod is 22 mm wide and the two of them screw directly onto each other.
The center pin from the tank usually contacts directly onto the battery.
Perhaps in a couple years something like a 22mm interface will become a standard or maybe it will be 23mm or 26mm or 30mm.
Because the hybrid has no 510 connector part, they are often shorter than the regular mod.