From the manufacturer:
Put a wow effect into your extra-special notes with the Gelly Roll Silver Shadow Gel Pens. With a patented design, these pens lay down a silver line shadowed with a color. Use on porous, bright white paper for best results perfect for fine invitations. The dye-colored inks dry instantly and are non-toxic. Meets ASTM and ACMI non-toxicity standards and is AP seal certified.