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

Smooth. The ones I got are smooth. However, there were some issues, once I took the carriages off for installation and tried to re-insert them back onto the rails. The ball bearings popped out like mustard seeds in whole grain mustard. The retaining wire is. sufficient, so long as the carriage is on the rail. I noticed that there were gaps in the ball bearings, so these carriages probably weren't filled to the max.Having said that, they work well. Good price for a decent product, just not a top notch product. Need to handle with care or be prepared to buy some extra ball bearings to refill in case of bearing losses.