Heat insert question

What are the best or most commonly used sizes of heat inserts. 2mm, 3mm, 4mm, 6mm ETC.

I have mainly used 2 and 3mm inserts.
Bigger may be needed for commercial parts.

Not being metrically inclined, 2mm is the OD of the thread?

Yes, see attached chart.

I use mostly M4 size. It really depends on what you do. M2 is too small for most of what I make but then @HobbyMaker3D suggests they usually use M2. Personally I make mostly functional parts M4 is about 5/32, M2 is 5/64.

I’ve mainly used M3 in building my Voron 2.4. I used a few M2’s on my Klicky PCB.

I use 3mm, 4mm, 5mm and 10-32 heat inserts. The size I use depends on the use case for what I’m printing.

I as wondering what to stock up on and I don’t want a lot of unnecessary sizes. Thanks for the info.