I use the MMVAPORS genuine DID20 holds 3.5ml of
e-liquid has wick hole of 3.5ml for the stainless mesh wick and 32g Kanthal A1 wire.
Nothing fancy but have tried most clones out there and their simply not as good period such as with the gaskets, center pin, machining,and placement of the wick hole not being right up against the positive pole frustrating folks getting hotspots.
There expensive bought new but sometimes in the classy's they can be had for a decent price just make sure they have not been tampered with such as enlarging of the airhole.