Levasil® FX401 is aqueous dispersion of modified colloidal silica. The silica dispersion is sterically stabilized, and the amorphous silica particles carry a negative surface charge. The silica particles are discrete, have a smooth, spherical shape, and are present in a narrow particle size distribution. The physical appearance of the dispersion is a translucent liquid, slightly more viscous than water. Levasil® FX401 is produced for world-wide distribution.