Macro that should create csvs of all the sheets of a workbook doesn't work! help!

Sub Make_New_Books()
Dim w As Worksheet
Application.ScreenUpdating = False
Application.DisplayAlerts = False
FileExtStr = ".csv": FileFormatNum = 6
For Each w In ActiveWorkbook.Worksheets
w.Copy
With ActiveWorkbook
.SaveAs Filename:="C:\8350\" & "8350" & "_" & w.Name & FileExtStr
.Close
End With
Next w
Application.DisplayAlerts = True
Application.ScreenUpdating = True
End Sub

The line that is throwing an error is ".SaveAs Filename:="C:\8350\" & "8350" & "_" & w.Name & FileExtStr
.Close"