Atd Tools 2181 Dual Piston Straight Line Sander, In Great Working. Fast Free Shipping .. This ATD Tools straight line sander is a powerful and efficient tool for automotive sanding and smoothing. With its dual piston design, it quickly delivers a smooth finish on any surface. The sander features a 1/4in. air inlet size and is perfect for automotive repair and restoration projects. Fast free shipping is available for this item, so order now and get started on your next project!