I vape mtl rather frequently.
Really it depends on what you want to spend.
You can get the Cthulhu mtl (24mm diameter) for under 35$ it's a great so for coil RTA with inserts to adjust the size of the airflow.
The serpent mini is more of a so flexible coil restrictive lung hit in my opinion.
After 4 years of vaping mtl though, I always go back to the same 3
The kayfun lite or kayfun 3.1-both 22mm diameter.
The light doesn't have adjustable airflow the 3.1 does but it goes from tight to tighter.
The lite is really ideal for most and it's cheaper. (You can find them from 60-90$) they are easy to build and have been around for years so they don't have to fill. What they do have is that they set the bar for rtas and are still relevant for mtl vapers. There are plenty of accessories too.
I'm selling my kf4 and keeping my 3.1, if that tells you anything.
Another good one for me is the kayfun mini v3. It's small but on a small mod it fits in the little pocket of your jeans.
It's what I'm using today.
They are easier to build on, have top fill and are very small about 17mm diameter where 22mm is or was the standard.
My other favorite mtl rta was the taifun.(22mm diameter) It's tall a little tricky to build on at first but it is a flavor machine for a good wet vape. It's very tall though so if you're using a tube mod it may look like a light saber.
Lastly theirs the erlkoenigin. A very nice very pricey RTA at 21mm and about 160$. It is beautiful and a fantastic piece. It's a little tricky to wick but it has the best flavor from any of my tanks. It also has topfill. My only advice with it is that for the money you can get two kayfuns and save time and stress with the build and wick process. Plus the ability to customize it as you want with all the accessories out there.
Sent from my XT1650 using Tapatalk