AMMO by MIG Paint Brushes - Brush Painting for Modelling
Item: #8 SYNTHETIC SAW BRUSH

From the Manufacturer:

This brush is specifically designed to perform dirt and streaking effects. With it we will be able to draw irregular lines obtaining a very realistic finish.
The Synthetic Brush range made of high-quality fibers, offers great spring. They are solvent-resistant and can be used with any paint type including acrylics, enamels, and oils. These are heavy duty brushes at a very economic price, making them a great option for all types of painting and weathering techniques and tasks.