CtrEditor/ObjetosSim/ucBotella.xaml

<UserControl x:Class="CtrEditor.ObjetosSim.ucBotella"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Ellipse Height="{Binding Diametro}" Stroke="red" Fill="Gray" Width="{Binding Diametro}"/>

</UserControl>