All my Polydryer boxes have quick-connect fittings for 6 mm tubes. The only annoying thing is that the release ring is a bit fiddly, so I designed this handle.

You need:

• Festo QSMS-6 Pneumatic quick-connect fitting
  there are similar connectors available from other manufacturers or aliexpress
• M3x30 grub screw (or any other kind of M3x30..35 screw)

Print settings:

• PLA
• PrusaSlicer print profile “0.25mm STRUCTURAL”
• 15% Infill