Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5466553.

The T12 soldering iron doesn't fit correctly in the Hakko FH-300 soldering stand as it sits at an angle and the tip of the soldering iron will touch the bracket inside the FH-300 stand.

This prevents that from happening and allows the soldering iron to correctly sit in the FH-300 stand. This adapter has a notch added so it can't spin and will seat correctly, snug push fit onto the FH-300.

Check pics to see fitment.