jasntruss,the light duty of ladder truss,triangle truss,square truss have standard size,such as 250*250mm,300*300mm.The medium–dutytruss have 400*400mm,450*450mm,500*600mm.The heavyduty truss have 520*600mm,600*760mm,520*1000mm have two connector ways:one is square connector,another is aluminum board connector,it made of the diamiter 50mm as main tube,and diamiter 30mm as inside tube beside the light –duty used diameter 20mm which have large loding capability for used in heavy project.