Complete Linear Rail Kits: This linear rail set includes 2pcs 39.4 in / 1000 mm long SBR20 rail shafts and 4pcs SBR20UU blocks. Sliding blocks are used cooperatively with rails, smooth sliding provided by the inside linear bearing. High-Quality Steel Material: CNC parts linear rails are made of carbon steel, linear bearings are made of quality bearing steel with aluminum alloy housing. Surface chrome plating treatment beautiful anti-rust, high hardness, more durable. Premier Linear Guiding System: Perfect combination of the main axle bearing rail and aluminum alloy support, which nicely stabilizes the original rail. Industrial-grade standard SBR block, with a high precision linear bearing inside. Easy to Install: Conveniently install the linear rail by aligning the track with the mouth of the slide rail and pushing the slide rail until the slide rail completely falls. It's no need for maintenance. Wide Application: The linear guide rail is widely used in automation machinery such as DIY CNC routers, lathes, machine tools, bending machines, laser welding machines, etc. Also, applicable for large-scale transmission equipment, including industrial robots, cracker machines.