Packs of Black and White 3mm Flash Cards 

Please note that the veneered Black and White is only on one side, and the other is standard MDF brown 

The White has a slightly porous texture, so Drywipe Pens do tend to leave a slight smear on them. When testing, I found Coloured Chalk Pens to be better, as I could remove most of the ghost leftover with a baby wipe, and then dry cloth

The black is easier with the Chalkboard pens, and perfect with Stick Chalk. A wipe removes the marks easily.