I just finished calipering ID of a bunch of driptips..Now if I could solve the wide bore tip issue without simply using an "aftermarket" tip.
Kanger subtank mini stock wide bore is 4mm inside dia
TFV4 tip thats got 2 layers is 5mm
Merlin is 5.9mm, I don't like that one at all.
I also measured a bunch of random tips mostly stainless and the rainbow metal and most were 3.9 and 4.0mm. I did come across a older swivel plastic tip that was 4.2mm. Those long curved tips were 3.2mm. A couple of the plastic vase type were 4.2mm. A glass vase was 4.5mm but the opening at the top was 2.9mm. Generally speaking since I'm able to vape nasty low coils with a 4.0mm subtank tip, thinking it was wide bore in which it isn't there should be no problems using other tips...I never thought of measuring ID if driptips until just now.
Just for kicks I'm vaping a .25 SS clapton at 40 watts in a Merlin with a Istick100 using a glass vase tip and having no airflow problems and it can handle it as fast as I can pull.