Review on Iverntech MGN12 700Mm Linear Rail Guide With 2 MGN12H Stainless Steel Black Carriage Block For 3D Printer And CNC Parts by Tony Stennis

Two of the 3 I ordered slide smoothly with even the slightest tilt (15°) of the rail. The 3rd is pretty much unusable it has so much drag. You can hold the rail completely vertical and it still doesn't move on it's own. Upon close inspection, we can see that the precision on the carriage is significantly off so it's off center on the rail causing too much pressure on one side including having the retention wire bottoming out on the inside of the rail channel. I confirmed it's the carriage and not the rail because the other 2 carriages glide just fine on the same rail.Update: Seller/Manufacturer sent me a replacement quickly and without hassle as soon as I notified them of the defect. Replacement glides smoothly and quietly. Frustrating to get a defective part but it happens. At the end of the day, I ended up with 3 perfectly working rails so I'm happy.