Thanks for letting me know!
I bought something like this off Amazon and it actually ended up being a bit loose; it bottoms out before the heads seat in the exhaust adapter.
Then I bought some 3x15 ones and they’re too short… 
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Ack, the adapter I used must just have used the right length for those screws and I got lucky! Junior hacksaw the ends of the threads off, job done. 
Circling back for Japan, in case anyone else stumbles across this thread: I used these M3 x 18 ones and they fit perfectly.
I can confirm these screws fit. I used a printed right-angle exhaust mount from Maker World. It was 15.4 mm thick. That gave me 4.6 mm of screw sticking out. The hole depth on the printer seems to be about 10.7 mm.
Also, I believe it was the YouTube channel Functional Print Fridays that created an exhaust shroud that uses alignment pins and magnets if you don’t feel like going the screw route.
I reached out to Bambu support, pointing out the difference between (at the time) their screw kit page and the laser module guide in the wiki.
At the time, the laser module install page showed BT 3-20 screws (self tapping - more sheet metal like), whereas the screw kit page shows BTG 3-20 (machine) for attaching a vent pipe. They told me the correct screw is BTG 3-20, but they do not have them for sale in their store (they have since updated the laser install page). Does anyone have specs on these BTG 3-20 screws? Are they normal 3mm x 20mm machine screws? Thanks!
(I did try to include links to the two pages referenced, but my post wouldn’t go through with them)
I finally got my hands on the BTG3-20 screws (machine threads), but they slide in 8mm and then stop / bottom out. Almost like something in the printer is stopping them. Is there some trick to getting the screws to bite? Note that my H2D is the non laser version if that makes any difference. Thanks!
so the screw hole is clearly unthreaded plastic. Several of the screws that come with the unit fit these holes depending on the depth of your print.
I was looking for a screw to fit in the rear panel for a generic poop chute for my P2S. I kept forgetting to add the screws (BT3-8) to my orders from the Bambu site so I looked around my loose screw bin for a 3mm diameter screw with the same thread pitch. Lo and behold I found one that fit perfectly - it came from an old plastic kids toy. I have a habit of taking all the screws out of toys and other miscellaneous items that are being tossed into the trash. So basically many generic plastic toys use this type of thread forming screw.
Hi - I was wondering if you have since found he exact answer for these 4 screws? I’m 12 and struggling to find them. I’m not seeing them in the clamp bag like others have said. I have the H2C.
Am not allowed to paste a link herebut you will find a very simple, clear comparison of BT3 vs M3 by going to BAMBU LAB WIKI and searching for article titled… A Practical Guide to Screws for Bambu Lab Printers.
Still searching fir where to buy other than Bambu. Otherwise, I’ll buy from Bambu on next Bambu filament order size that triggers free shipping. No bigggee..
Let me know if alternate source found.
edit: my bad, they are in the bag with the clamp…
Thank you, thank you, thank you. I’ve been searching everything - supply box, tool box, couldn’t find them. As you said, they were in the bag with the clamp, which is the last place I would’ve looked.