... for round or square ducts 2,Handle round/square size:12.2m Item NoProductSpecificationFinishQty/box20503Damper RegulatorRound 12mm,10MM,SQR 12MM,10MM,L ... system,suitable for round or square ducts2Handle round/square size:12.2mm,12.5mm3It's avaiable for round or square spindle4Finsh:galvanized ...