Descriptions:The linear slide rail shaft is made of high quality carbon steel, and the bearing block is made of aluminum alloy, sturdy and durable.Perfect for your DIY CNC routers, no more unwanted errors in your machining workmills, lathes.Features:Thelinear slide rail shaft is made of high quality carbon steel, and the bearing block is made of aluminum alloy, sturdy and durable.Industrial-grade standard SBR block, with high precision linear bearing inside.Surface silver plating treatment, beautiful anti-rust, hardness can as high as HRC62, more durable.The adjusting handle can adjust the tightness of the slider.Standardized processing, ideal for guide rail positioning.Perfect for your DIY CNC routers, mills, lathes.Aluminum alloy support rail with pre-drilled holes for ease of mounting.Specifications:Material: high carbon steel,Aluminum alloyModel: SBR12Rail shaftlength: 400mm / 15.75inchRail shaftdiameter: 12mm / 0.47inchBlock inner diameter: 12mm / 0.47inBlock outer diameter: 40mm / 1.57inWeight:1900gPackage Included:2 x Linear Slide Rail Shaft4 x Bearing Slide Block .