Pack of 7 High Quality RJ4JP-01-08 Sold polymer Linear bearing a direct replacement for the metal LM8UU bearing commonly used in many 3D Printers. Perfect replacment for the X and Y axis on 3D printers. Ideal for RepRap, Prusa, Mendel, etc. Product Specification: 8mm Inner diameter. 15mm Outer diameter. 24mm Length.