It seems that there are no issues using Scripting.Dictionary #include <Array.au3> Local $a[11] = [1, 1, 3, 5, 6, 7, 8, 9, 10, 11, 12] Local $b[12] = [1, 2, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14] Local $sda = ObjCreate("Scripting.Dictionary") Local $sdb = ObjCreate("Scripting.Dictionary") Local $sdc = ObjCreate("Scripting.Dictionary") For $i In $a $sda.Item($i) Next For $i In $b $sdb.Item($i) Next For $i In $a If $sdb.Exists($i) Then $sdc.Item($i) Next $asd3 = $sdc.Keys() Fo