MGN12H Miniature Linear Rail. MGN9H Miniature Linear Rail. 【Drop Proof Rubber】：There are 2 black rubber stoppers on the ends of the linear sliding guideway in case the carriage falls off the rail. 【Premium Material】：The linear bearing is made of heavy-duty bearing steel,which is more durability, high stiffness stiffness,high accuracy,smooth running, low noise than others.