this is what the website says abut them.... Exclusive Inks® Stamp Pads Our Exclusive Inks® stamp pads offer an innovative in-lid pad to keep ink close to the surface. Labeled on three sides for quick reference, each pad is stackable, closes securely, and features a patented swivel base for easy access to the entire pad surface. Each is approximately 3 1/8" × 4" and contains dye-based or pigment-based ink that is vivid, luxurious, and true in color. It’s also archival safe and pH-neutral. Refresh a used stamp pad with a matching re-inker, available in every Exclusive Inks color.