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 accuracy 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, perfect for guide rail positioning. Perfect for your DIY CNC routers, mills, lathes. No more unwanted errors in your machining work. Aluminum alloy support rail with pre-drilled holes for ease of mounting. Specifications: Material: high carbon steel, Aluminum alloy Model:SBR12 Type: slide guide Glide path: linear guide Rated dynamic load: 860 Rate static load: 1370 Accuracy grade: H Fixed bolt size: 8 (mm) Fixed mode of sliding block: Locking type Allowed static torque : 1 (kn.m) Rail shaft length: 30cm/11.8inch Rail shaft diameter : 12mm/0.47inch Block size: 4 x 4 x 2.8cm/1.57 x1.57 x1.10inch Maximum Load: 30KG Weigh t:1316g Package Included: 2 x Linear Slide Rail Shaft 4 x Bearing Slide Block .