Rows will provide you the rows, as mentioned in the comment. And Columns will provide the columns for you.
Dim col As Range
For Each col In rngSize.Columns
Dim cell As Range
For Each cell In col.Cells
MsgBox cell.Value
Next cell
Next col
A second way would be to copy the values of the range into an array
Dim vDat As Variant
vDat = rngSize.Value
Dim i As Long, j As Long
For i = LBound(vDat, 2) To UBound(vDat, 2)
For j = LBound(vDat, 1) To UBound(vDat, 1)
MsgBox vDat(j, i)
Next
Next