A MOD also known as a modified electronic cigarette has become a huge hit in the electronic cigarette scene, especially with China now producing these mods as well, they will become more known, cheaper and easier to come by. A MOD usually consists of a small tube or box that houses a bigger battery than you would normally see on an electronic cigarette. These MODS use different names and combinations of what battery they use. I Strongly recommend only using PCB protected batteries as recently there have been numerous reports of mods exploding mainly due to using unprotected batteries.
Some MODS have different placement for the switch to activate the device. If the device is a box mod, the switch is usually located on the side of the mod and if it’s a tube mod, the button is usually located near the middle of the device or at the bottom. The buttons tend to be placed in a location where your thumb will rest. A MOD will have batteries that last longer than normal electronic cigarettes and some may be a higher voltage or even a variable voltage.