The Wishy Washy markers are filled with liquid chalk and are suitable for all smooth surfaces (glass, painted surfaces, plastic, etc.), as well as for whiteboards, blackboards, and chalkboards. They are particularly a great addition to the chalk coloring book. The drawings or writings dry in less than 30 seconds and can be wiped off at any time with a damp cloth. On glass surfaces, the color can even be removed with a dry cloth. It's simply a fantastic invention. The colors are bright and vibrant, making it a lot of fun to paint with them. The pack includes nine markers in bright colors: pink, orange, red, yellow, turquoise, blue, purple, black, and white. The markers are non-toxic, odorless, and quick-drying. They are suitable for ages 3 and up. Dimensions: The marker tip is 4.5 mm.