<Window x:Class="ScrollBarCustomThumbSize.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:sys="clr-namespace:System;assembly=mscorlib" Title="" > <Window.Resources> <Style TargetType="{x:Type Slider}"> <Setter Property = "Background" Value = "Red"/> <Setter Property = "IsSnapToTickEnabled" Value ="True"/> <Setter Property = "TickPlacement" Value ="BottomRight"/> <Setter Property = "AutoToolTipPlacement" Value ="BottomRight"/> <Setter Property = "TickFrequency" Value ="1"/> </Style> </Window.Resources> <Grid> <Slider></Slider> </Grid> </Window>