1 x 450mm/17.71" Linear Rail,1x MGN12H Carriage Blocks.Linear Guide Rail adpots blackening treatment on surface to prevent rusting in long-term use. Rail Guide Material: Heavy-duty bearing steel,smooth running,low noise. MGN12H Carriage Block Material: Stainless Steel.Blocks are pre-loaded. Suggested to use M3 T nut and screws if you fix it to 20 series EU Al-profile.There are two rubber stoppers on each side of the linear rail to prevent the sliding block from falling out. The linear guide are small size and light weight,especially suitable for miniaturized equipment,such as routers,3D printers and plasma cutters etc. 1 x 450mm/17.71" Linear Rail,1x MGN12H Carriage Blocks.Linear Guide Rail adpots blackening treatment on surface to prevent rusting in long-term use.