Ultratop 50 singles , often called Ultratop 50 , is the weekly chart of fifty best-selling singles in Flanders , Belgium . Ultratop 50 and is produced and published by the Ultratop organization . Ultratop 50 singles , often just Ultratop 50 , is the weekly chart of fifty best-selling singles in Flanders , Belgium , and is produced and published by the Ultratop organization .