2Pcs SBR12 200mm Linear Slide Guide Shaft Rail 4Pcs SBR12UU Bearing Block CNC Parts 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. 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: 200mm/7.87inch Rail shaft diameter: 30mm/1.18inch Bearing Block size: 40*40*26mm/1.57*1.57*1.02in Weight: 991g   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.