National Detroit is one of the best tools in the world.  They invented almost all of the popular sanding tools in use today.  If you are a professional, they are the brand of choice for high use situations. All National Detroit tools come with a manufacturers 1 year warrantee.

The purpose of an air file is to save time.  It can take up to 75% lless time to do work on long straight areas with this tool, than with a DA sander.  It also helps to keep the work straight and flat.The National Detroit air file (also called a longboard), is unique. 

Unlike most air files from other manufacturers, which just go back and forth, this tools is also a random orbital sander.  This gives you the best of both words.  There is a better finish because there are less paterns.The standard tool comes for use with clip-on paper (17 1/2"), but it can be special ordered with a sticky (16 1/2), or hook and loop pad.