Filler Powder (Q-Cells) are white microscopic glass spheres that can be added to our world famous 421 Epoxy Resin. Once the resin has cured with the filler powder embedded in it, upon being sanded, the microscopic spheres explode. Therefore, you can produce your own filler with it's own consistency. You can add the Filler Powder up to 4 times the volume of the resin. The more filler powder added to the resin, the more bulked up the with the powder the mixed solution becomes and has the effect of being easier to sand. (ie: softer)