2-Pack T8 Lead Screw with POM Nut for Prusa I3 MK2/MK2S/MK3/MK3S 3D Printers - High Precision Z-Axis Upgrade for Smooth 3D Printing Performance (Perfect for DIY Repairs & Printer Maintenance)

These are good quality and immediately worked well in my MK3S+ clone. I had to replace both of the originals in the clone kit since it was too tight and one was too loose. With these nuts there are two things to be aware of. Firstly, the ones received were not exactly the same as in the photo (or the originals). Not all of the four mounting holes are the same: two of them are smaller and threaded. I guess they can be used for other printers too. Secondly, the four screws provided are M3x10 (as per the photo) but the Prusa MK3 requires M3x18.