1.After the ink has dried on paper, it is waterproof. Water-based with stamp ink, easy to wash off. Non-toxic and harmless, it will not harm the child's health. 2.Can be used as finger painting to promote hand-eye coordination, imagination, creativity, ability to express nature and freedom in children. 3. Each ink pad can be stacked for easy storage. This not only keeps the ink safe, but also keeps the sleeves neatly stacked so you are always tidy in the play or work area. 4.Gifts suitable for children, children exercise creativity, learn good colors from toys. Also suitable for diy arts, crafts, business card, scrapbook, wedding decoration, etc. Technical data: Material: sponge, plastic, non-toxic water-based ink pad Single size e: 4 x 4cm / 1.57 x 1.57 inches Color: As shown (20 colors) Package includes: 20 x ink pads Note: Because of the more sensitive sponge. If you think it is relatively dry, we recommend adding a small amount of water, which can be around 2 drops.