<<Style TargetType="RadioButton">
        <Style.Setters>
            <Setter Property="Height" Value="18"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="RadioButton">
                        <BulletDecorator Background="White" Cursor="Hand">
                            <BulletDecorator.Bullet>
                                <Grid Height="16" Width="16">
                                    <Border Name="RadioOuter" Background="Transparent" BorderBrush="Gainsboro" 
                                            BorderThickness="2" CornerRadius="2" />
                                    <Border CornerRadius="0" Margin="4" Name="RadioMark" Background="#FFADADAD" 
                                            Visibility="Hidden" />
                                </Grid>
                            </BulletDecorator.Bullet>
                            <TextBlock Text="{TemplateBinding Property=Content}" Margin="5 0 5 0">
                            </TextBlock>
                        </BulletDecorator>
                        <ControlTemplate.Triggers>                           
                            <Trigger Property="IsChecked" Value="True">
                                <Setter TargetName="RadioMark" Property="Visibility" Value="Visible"/>
                            </Trigger>
                            <Trigger Property="IsChecked" Value="False">
                                <Setter TargetName="RadioMark" Property="Visibility" Value="Hidden"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style.Setters>
    </Style>