K1 top head set spacer for Dengfu frames. STL for download. 
Print from PETG, layer height 0.125mm. 3D printed fit perfectly (depends on printer calibration) and tested for 2 weeks with no issues. After removing we did not see any cracks or bends.
CNCed part from aluminium was liitle bigger OD and had to sand it down a little to fit into frame.