What it is:

The Skewer is an open-source high performance T-Pull blaster by Charamile Designs (Taffy). This listing is for the hardware required to build one using 12 in standard barrel. No printed parts are included.

Links: 

• Build instructions
  
• Printed files

Note:

 Charamile Designs (Taffy) is the designer of the files and BOM, Silver Fox industries is the maker of this hardware kit.