LUHR Ball Bushes Block Sets - Closed Supplied with LBBR linear bearing, with integral seals (2LS models), and have extruded aluminium alloy housing. SKF Linear Ball Bushings & Sets Closed ball bushings and plain bearings for XY positioning, pick and place applications and precision linear motion systems.,Plain bearings to be used in heavy shock, vibration, high acceleration or high speed situations which are unsuitable for linear ball bearings.,Note that higher frictional forces must be expected with linear plain bearings.,Ball bushings comprise a cage, in which the balls are guided, along with the raceway segments and integral seals,Further axial securing is often unnecessary when linear ball bearings and linear plain bearings are pressed into a J7 or J6 tolerance hole.