I designed this for a Christmas bill tube to give as a gift, with cash.  I found after the fact that it also holds nickles well.  So enjoy it how you will.  A note.  I designed this with a fairly tight thread tolerance of .025 inches.  This works flawlessly in ABS on my Taz5.  It didn't work so well on my MakeIT pro in PETG.  The internal threads and small layer cross-section can make for mushy prints, so I recommend if you are having issues with the threads turning cleanly, either scale up the cap in x and y a tiny bit (5%)  or print 2 of them.  I printed these at .2 mm layers