simply a replacement end cap/plug for the bow flex knee pads that allows you to hang the cables when folded up so they are not just loosely crumpled up an the floor. 

It's designed to use flexable fimaments use a mid 25-50% infill with a high 4 or more shell layers to obtain a good balance of stiffness and flexability. It probably would work with hard materials like PLA's and ABS's with some minor sanding/filing of the rings to fit the pipe.