How do I change the width of the Textboxes created for edit-mode of a Datagrid?

<asp:DataGrid id='DataGrid1' runat='server' AutoGenerateColumns='False'>
<Columns>
<asp:TemplateColumn HeaderText='ProductName'>
  	  <ItemTemplate>
		    <%#DataBinder.Eval(Container.DataItem, 'ProductName').ToString()%>
	  </ItemTemplate>
	  <EditItemTemplate>
		    <asp:Textbox runat='server' width='450' maxlength='450'/>
	  </EditItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:DataGrid>