# Needle
The needle is one of the indicator types, that the **RadGauge** control introduces. It inherits the **InteractiveIndicator** class and introduces some specific features.
> tip To learn more about the base features of the indicators read [this topic](https://www.telerik.com/products/wpf/documentation/controls/radgauge/features/indicators/basics).
Here is a list of the **Needle** control's specific features:
* [Tail Height](https://www.telerik.com/products/wpf/documentation/controls/radgauge/features/indicators/needle#tail-height)
The **Needle** control is represented by an arrow that points to a value from the scale. The appearance and the shape of it can be easily modified. To learn how read the Styling the Needle topic.
> tip You can change the background and the border color of the needle via its **Background** and **BorderBrush** properties.
> The **Needle** indicator should be used only in radial scales.
> Indicators should always be placed inside a **Indicators** property of the scale object.
Here is an example of a **Needle** definition:
```XAML
```
Here is a snapshot of the result:
## Tail Height
Gets or sets the relative height of the needle tail. You can change the height of the needle tail by using the **TailHeight** property. To calculate its height you'll need to substract the radial scale **Width** (0.1 by default) from the scale **Radius**.
```XAML
```
Here is a snapshot of the result:
