This is the paddle for a quarter-half-quarter wave plate - an in-fiber polarization adjuster. We use a Thorlabs' 780-HP fiber. We wrapped the fiber twice around the first and third paddles in the array, and four times around the second paddle. As with waveplates, by adjusting the rotational position of each paddle, the output polarization state of the fiber can be changed.
Diameter of the circular groove for the fiber is about 62mm. The OpenSCAD file the paddle was produced from is included and can be readily adapter to other groove diameters.