this is a housing for the short linear bearing used for most 3D printer tables. it can be a direct replacement for the aluminum housed linear bearing and will last for a long time. the linear bearing simply snaps into place and will not rotate in the housing. this is part of my improved rep rap project, with no zipties. this is also a complete remake and upgrade of my QU-BD TWO UP the new printer will be called the RAPTOR zero ziptie, 3D printer, the project will be on my forum http://irondmax.com/irondmax/forum/forums/forum-view.asp?fid=36 my youtube video of it https://www.youtube.com/watch?v=ixOHqhuBTiM