When your application calls for a tie-bar configuration, the A-series is your choice. MODEL SHAPE HEIGHT DESK A457 A 17.5'' 18''x24'' A407 - NBRK A 17.5'' 18''x24''OPTIONSLaminate Work SurfacePermaTuff EdgeBlack EdgePlywood Core Work SurfaceNon-Skid GlidesQ-Ball GlidesSteel Glides