Css for all dropdowns

Hi

  How to set font size , width etc for all dropdowns . All dropdowns are in tfoot.

                                            <td>
                                                <asp:DropDownList ID="ddlBook" class="form-control" required="true" parsley-trigger="change" runat="server" OnSelectedIndexChanged="ddlBook_SelectedIndexChanged" AutoPostBack="true">
                                                    <asp:ListItem Value="">Select Book</asp:ListItem>
                                                </asp:DropDownList></td>

                                            <td>
                                                <asp:DropDownList ID="ddlSession" class="form-control" required="true" parsley-trigger="change" runat="server">
                                                    <asp:ListItem Value="">Select Session</asp:ListItem>
                                                </asp:DropDownList></td>

Thanks