We've come a pretty long way with duct designs.  Each iteration is incremental but definitely an improvement over the previous version.  This latest version is a design that comes from a member of the community.  After much discussion and testing, this latest duct provides more thrust, lower noise levels and better durability than any previous design.  You can mix and match this duct with any of the previous designs on the same craft and it will fly well.

The member of the community which primarily worked on this design has chosen not to make themselves known but the print file is available for anyone to print.  We just offer the ducts to make it easier for those without printers.  These prints are also from a PTEG material that is fully heat stable and a bit more durable than other options for such a design.  The prints are imperfect at the outlet of the duct because it is not as easy to print this design.

Note: The ducts do NOT fit the frame perfectly on purpose. When screwed into place the ducts are held under tension and are somewhat oval. When fresh props are inserted, they will rub against that walls of that duct. Arm the quad and get the props spinning, then hover for a few seconds to allow them to grind into place.  It will be loud during this process and then it will quiet down considerably. This sort of fit actually improves efficiency a but but more importantly, reduces overall vibrations in the system because it's all held under tension.  Again, this imperfection is a biproduct of printing but also helpful.  There is no issue if the ducts do not fit 100% perfectly. 

Specifications:

• Improved ‘duct-foil’ for more thrust, better efficiency and no loss of control
• Printed from PTEG which is fully heat stable
• Durability is much better than PLA
• Brass inserts not required and no longer included
• ~13g per duct without brass inserts

STRONGLY Recommend:

- FPVCycle 23mm 3450kv motors
- 4S 1100-1300mah
- Gemfan 75mm triblade cinewhoop prop