20mm Linear Guideway System 55" Long Rail with 2 Built-in Trucks ItemShaftDimensions(mm) EhBHTFXYCS1S2 d1 x d2 x lPN SBR 20mmx55"20mm22.5274517.7519810305.55.5x9.5x5.4150mm20mm Designation Main dimension (mm)Ball bushing hEWLFh1Open AngleBCSLBall Bushing ItemBasic load rating dynamic (CN)static (CoN) 20mm Block w/Ball bushing232448503910603535M612LM20UUOP8821370 Complete linear guideway system with 2 blocks installed, you will get a 55 inch supported rail with 2 blocks, each block has an open ball bushing, that can make a smooth low friction cnc linear motion system.