Terra's have run on ego twists for me. Now, they take longer than rods and coils to heat up. This is simple physics. The wire is covered by ceramic in a donut. An uncovered wire would just need to get hot. One coated in ceramic must then heat the ceramic first before it gets hot enough and wax vaporizes. So per hit, a donut takes more time and energy. You will charge your ego battery far more often with a donut. So... they work but they work better on bigger mods. Coil and rod attys can be more easily configured to run on the smaller batteries. In short, a twist will work, but you are nowhere near the potential wax pens can have until you get a better battery mod.