If all 4 worked as well as 1 of these would be a 4 star purchase. As mentioned, not all of the mounting holes were drilled correctly - not that they weren't cut correctly, but that some of the holes were milled at the widest point of the rail. The screws still hold them in place, but a few bad holes have less than half the threads. That alone should have been my signal not to buy them. 3 out of 4 - junk. They aren't smooth when not under load, they feel better when you press them against the rod (force flattens the internal bearings), and they stick when you have a fast servo combined with a hardware plate that doesn't hold up evenly across all stocks.
Goodyear Ультра Грип Айс СУВ 235/65 R17 108Т (Зима)
35 Review
Iverntech MGN12 700Mm Linear Rail Guide With MGN12H Stainless Steel Black Carriage Block For 3D Printer And CNC Parts
9 Review
Iverntech MGN12 400Mm Linear Rail Guide Upgrade For Ender 3, Corexy, Tronxy, Delta Kossel 3D Printers And CNC Machines With Stainless Steel Carriage Block
12 Review
Iverntech 400Mm MGN12 Linear Rail Guide With 2 Black Stainless Steel MGN12H Carriage Blocks For CNC Parts And 3D Printer Upgrades
8 Review