If you have ever had the feather edge of your filler start peeling up on you when you are sanding it on a plastic part, then Polyvance's Filler Prep is a "must have" product. This isn't just any regular adhesion promoter. It's a highly concentrated adhesion promoter designed to withstand the peeling forces of sanding. This 4 fl. oz. (118 ml) can contains a built-in duaber to apply the adhesion promoter.