Easy to Use and Clean: Simply twist the bottom of the watercolor brush inwards or the top outwards to open the brush and fill it with water (intentionally, hoping your child won't be able to unscrew it and spill water everywhere), easy to use. And you just need to wash it with water after use, easy to clean. Suitable for water-soluble pigments, inks, and so on, easy to use, saving you a lot of time and energy. Leak-Proof: This solid watercolor brush is designed with a valve, preventing leaks during painting. With leak-proof, self-moisturizing, lightweight, and waterproof features, it is sturdy, portable, and convenient to carry for sketching and painting on the go. Material: This watercolor brush set is made of high-quality plastic pen body and transparent nylon hair brush bristles, ensuring the watercolor brush remains intact and does not spray, spread, or smudge during use. Non-toxic, safe for children, you can rest assured letting your children paint with our water pen set. Wide Application: These brush pens can be used well for a variety of occasions, such as ink crafts, watercolor works, watercolors, powder pigments, unfired watercolors, crayons, water-soluble pens, acrylics, gouache, inks, etc., decorating walls, living rooms, wallpaper, clay, windows, suitable for students, artists, teenagers, and so on, you can draw the finest line or color large lines, blend colors, and create new shades.