This is an adapter to fasten the 8mm lead screw with a 608zz bearing leaning on the 8mm rod. It avoids the lead screw touching the steel chasis while the bearing keeps it free to rotate but fixed into position. It press fits on the 8mm rod for a tight fit like the 608zz. Maybe you will have to file it a bit, remember it's a tight fit. Has been working like charm for me since I installed it months ago. Recommended to print it on PLA, it won't have heat stress and rigidity is the goal here. As you see in the picture there is also a Z top cap to fix the 8mm rod in place. I also include the STLs of this new version of the Z tops.