PEPIN Postcard Watercolour Books contain 16 cards, made of the finest acid-free watercolour paper. The 250 gsm paper is quite thick to make the cards suitable for mailing. The 16 colouring cards are made of the finest 250 gsm acid-free water colour paper, a joy to colour with a wide range of techniques, such as colour pencil, crayon, pastel, ink, water colour, etc.PEPIN Postcard Colouring Books match the quality of the finest professional watercolour pads. In order to get the best results, we recommend you use high-quality colouring materials.