4" Round or Square 40 pt. (1.0 millimeters) coaster printed on white pulp board. Biodegradable, recyclable, and environmentally safe with soy inks, these compostable pulpboard beverage coasters are durable, warp resistant, and color fast. While absorbent, this hard mat world-class coaster board allows for the highest quality multi-color graphics. With STURDY coasters you get economical full-color printing on both sides in low quantities starting at just 2,500.