Uni Liquid Chalk Markers utilise water-based pigment ink so you can mark on windows, glass, mirrors, plastic and metal surfaces with ease. The ink won't wash off in the rain, yet is easy to remove with a damp cloth. For permanent application the markers can also be used on chalkboards for a bold statement. Each marker has a 2.5 mm bullet tip. The markers are ideal for signage and can be used indoor and outdoor. The ink is made using a water-based formula and each colour is vibrant and opaque. This marker contains black ink. It's recommended to store these markers horizontally when not in use.