螺母，Z 軸

The left-hand threading is unusual, but it makes perfect sense once you see how it locks into the assembly jig. My machine’s Z-axis moves smoothly now with zero play.

I was pleasantly surprised by how precisely this nut fits the Z-axis screw. It's clearly made to a high standard, and the left-hand thread design really requires careful handling, but the end result is perfect. The unthreaded state makes sense now that I've seen how it's assembled.

Took my time reading the specs before buying, so the unmachined nut wasn't a surprise—it's clearly meant for factory assembly with that special left-hand tap. Fits the Z-axis screw perfectly once threaded, and the precision is spot on. Exactly what my build needed.