This is yet another filament holder for the Wanhao D6 with bearings. The designs I tried didn't work with my cheap 608 bearings as putting pressure from only one side would lock them up. The spacer tube in the middle and the small washers prevent this in the new design. The large tube only makes contact on the outside of the bearings so all can move smoothly. Used a 9 cm M8 screw (or 5/16, 3.5 inch), washer and nut I had around to hold this together. Use the original holder nut that came with printer to attach.