They are a very fine filamentous powder, with a low specific weight, white in color, which added in a small proportion (10-12% by volume) to the compound resin (A + B), slightly increase its density and make the bonding parts more filling like the locks, the joints, etc., and maintaining a greater quantity of resin, it gives it to the wood, which has the possibility of absorbing it and forming a more homogeneous and resistant joint.