filament return pulley for Vellemann Vertex 3D Delta K8800

For some kind of filament spools it is necessary to have a return pulley.
You can use 2 M4x16mm countersunk screws for the riser to fix this. I used 2 608zz bearings

UPDATE:

an improved version better for large spools. It reduces the problem that the filament stays in the gap between pulley and printer top.