# Filter Select
This operator is used to select faces of certain sizes relative to their shortest edge. It is particulary useful for **Random Loop Extrude**, **Random Panels** and **Panel Insets** where the panel islands often consists of thin faces with boundary edges.
Figure 1
When used, you will be shown the redo panel that will wait for your input in order to function. Here are the different redo properties and what they do:
{% hint style="info" %}
*This will only work if you have faces selected and will filter select these face selections.*
{% endhint %}
### Limit
This setting allows for the selection to be limited in the following ways:
* **None:** There are no restrictions on the selection.
* **Non-Manifold:** This limits the selection to faces that have no boundary edges.
* **Only Non-Manifold:** This restricts the selection to faces that have boundary edges.
Figure 2
### Length
The shortest length an edge can have in a face before being removed from the selection. Use this to deselect really thin slices of faces when you want to randomize an area because this can result to geometric spikes when used with some of the random operators.
Figure 3
### Linked Flat Faces
This will allow the remaining faces from the selection to include faces that share their normal angle sharpness threshold.
Figure 4
This is useful for organic surfaces to reselect some faces which did not meet the length threshold and were removed from the selection but still keeping most thin faces unselected.
### Sharpness
This only shows up then the **Linked Flat Faces** toggle is activated and will determine which faces are reselected based on the normal angle sharpness threshold of the selected faces.
### Select Invert
This inverts the current selection.
Figure 5
The **Filter Select** operator is very useful on a topology that has some thin faces you'd want to avoid like the meshes generated by [Random Starship](/add-ons/random-starship.md) or those that are created using the **Random Loop Extrude**, **Random Panels** and **Panel Insets** operator in **Random Flow**.
Figure 6
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