The Filbert paintbrush is a paintbrush used in artwork. It has a thick ferrule and hairs that are, on average, medium to long hairs in the shape of an oval. Filberts are particularly effective in blending work, usually of a figurative nature. Many artists agree that natural fibers work best for filberts because the hairs stick together better when wet.
The filbert paintbrush derives from the shape it resembles, that of a hazelnut with its namesake. This word comes from the Old French filbert, coming from noix de (nut of) Philibert. Philibert was a saint, (who died in 684), whereby the ripening of the nut in August coincides with his feast day.