These brilliant pens with a 4mm nib are permanent on porous surfaces such as clay, pottery, brick, stones, rubber, wood & glass. These are a fantastic range of multi-purpose fibre pens. Non-toxic colours, safe and light-resistant with perfect coverage even on dark or coloured backgrounds, they come with a super-durable fixed tip and ventilated safety cap. All colours are easily washed off your hands, but they may stain clothing. Perfect for small jobs, and even for preschoolers. 1 each Red, Blue, Green, Yellow, Black and White.