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 work mills, lathes. Features: The linear 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. Standardized processing, ideal for guide rail positioning. Aluminum alloy support rail with pre-drilled holes for ease of mounting. Perfect for your DIY CNC routers, mills, lathes. Specifications: Material: high carbon steel, aluminum alloy Model: SBR12 Color: Silver Rail shaft length: 475mm/18.70inch Rail shaft diameter: 31mm/1.22inch Bearing Block size: 40*40*26mm/1.57*1.57*1.02in Weight: 1823g Package Included: 2 x Linear Slide Rail Shaft 4 x Bearing Block Note: Please allow 1-3mm error due to the manual measurement. Thanks for your understanding. 1、The linear slide rail shaft is made of high quality carbon steel, and the bearing block is made of aluminum alloy, sturdy and durable. 2、Industrial-grade standard SBR block with high precision. 3、Standardized processing, ideal for guide rail positioning. 4、Aluminum alloy support rail with pre-drilled holes for ease of mounting. 5、Perfect for your DIY CNC routers, mills, lathes.