There it is vs a 1/8th in diameter drill bit. Anything larger it won't fit in without grounding against the top cap. Not sure how big it is exactly
This is a 22mm RDA they make 24mm and even 28mm RDA's but it'd look pretty goofy atop this box, it'd be hanging off the edges by 2-6mm. I could fit massive diameter coils in those but it'd likely perform poorly