The BlowerBrush is used to blow out sheetrock dust or bondo dust after sanding. If you do not blow out and brush at the same time, you are not getting all of the dust out. Getting the cleanest serface . This will give the plaster, compound, bondo, putty or primer the best surface to adhere to. If there is still dust in the sanding scratchs or crevices, the material that you put on top will not stick well. Allso when there is dust trapped under the bondo , putty or primer you will get heavy shrinckage on the finished surface. later on after the paint job is finished. The Blowerbrush conects to an auto shop air  compressour hose. It uses  standard autoshop  quick conect tool air hose fittings. Comes with a fully ajustable air valve for pressure and flow rate. Without the blower the brush cost $ 45.00 .dollars. The brush with the blower cost $ 55.00 dollars.