2Pcs SBR12-1000mm 12mm Linear Slide Rail Shaft 4Pcs SBR12UU Bearing Block Descriptions: The linear slide rail shaft is made of 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 work mills, lathes. Features: The linear slide rail shaft is made of 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 alloy Rail shaft length: 1000mm / inch Rail shaft diameter: 12mm / 0.47inch Block size: 39 x 40mm / 1.54 x 1.57in Weight: 3706g Package Included: 2 x Linear Slide Rail Shaft 4 x Bearing Slide Block