Linearführungen
Flachkäfigführungen
Flachkäfigführungen mit Winkel-Gleitbelag

Linear guidance systems
Flat cage guidance systems
Flat cage guidance systems with angled plain bearing layer

http://medias.ina.de/medias/en!hp.ec/Linearfuehrungen*0*Flac...

In addition they are composite materials: a steel shell provides the load capability of the bearing, the actual bearing layer deposited on it provides the good trobological behaviour as listed above.
http://www.kp.dlr.de/WB-RS/Erstarrung/web_eng/lager_eng.html

Kuzharov A.S., Bulgarevich S.B., Kuzharov A.A., Kravchik K.
Molecular mechanisms of self-organization during friction, part ii.orientational order of the bearing layer during self-organization under hydrodynamic friction conditions. pp. 173--179
Summary: A physical substantiation has been found how the structurization of the lubricating material resulting from the orientational order of anisodiametric particles in its composition (molecules and colloid particles) in the gradient high-speed flow which leads to the self-organization of the bearing layer and creates the minimal force of friction during hydrodynamic lubrication when the loading or the sliding velocity augment continuously.

http://www.ac.by/publications/trenie/tre22_2.html