We are using cards to mean smooth card (see below), and board to apply to thicker stuff. Apologies for confusion over any "in betweens".
We stock artists’ mountboards in a variety of colours, and greyboards & mill boards of various thicknesses. All our boards are available in several sizes, and thicknesses. We also offer a cut-to-order service.
More detailed information is available at busybusy.co and there are also suggestions and examples for use at busybusy.co/