<ItemsControl 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
    <Style TargetType="BItem">
        <Setter Property="Background" Value="White" />
        <Setter Property="HorizontalContentAlignment" Value="Stretch" />
        <Setter Property="VerticalContentAlignment" Value="Stretch" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="telerik:BItem">
                    <Grid x:Name="LayoutRoot">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="0.15*" />
                            <ColumnDefinition Width="0.7*" />
                            <ColumnDefinition Width="0.15*" />
                        </Grid.ColumnDefinitions>
<!--Qui va finito-->