Stooge for rubber winding.
It comes in two versions - for the Halftube and for the model.
I use two of them at the competitions - one for winding the motor in the Halftube and another to hold the model.
The stooges are modular - you can quickly disconnect the top hub and the bottom pin for transportation. All parts are interchangeable. You can see in the photo the two different heads, Pin, Struts and an Kevlar Cord.
The Strut is 12 mm diameter.