Thanks for explaining that Broose!
Unfortunately my PEEK tube just broke when I tried to unscrew the 0.5mm nozzle to switch back to the 0.35mm nozzle. I didn't realize how terribly designed the seemecnc hotend is until now, but I guess it's too late. The PEEK couldn't even take the torque of its own threads, and I was being gentle! I always printed at 240 degrees, so I don't think that weakened it. I thought that if I ever broke my hotend, it would be because of a dumb mistake like smashing it into the glass plate, not normal use...
I ordered my rostock May 16th and I still don't have a working, calibrated printer. I've spent at least a hundred hours over the last month and a half building, fixing, calibrating, ect, and nothing to show for it. And I've put ~1100 dollars into it (will probably be over ~1200 by the time I have it working again). At this point I'm starting to regret choosing the rostock.
I'll probably get the E3D all metal hotend, but I'll have to get a replacement PEEK tube so I can print a mount for the E3D. If there are any problems with the E3D or if there are better metal hotends, please let me know!
EDIT:
I just noticed that the PEEK tube is glossy black on the inside and the threads are broken off so that the bottom part is stuck inside the lower aluminum piece. I hope I can get it out...