Linear bearings are used for linear motion. They can be used to build low cost and simple linear guiding systems for a wide variety of applications such as CNC and 3d printers. This linear ball bearing slides along an 12mm linear shaft. 

Specifications

• 30mm long x 21mm outer diameter x 12mm inner diameter
• Dynamic load rating C(N): 510 N
• Static load rating Co(N): 784 N
• 4 Ball races inside
• 2 grooves with 20 mm outer diameter