They're called Coals (9789464043099)

Cooking and grilling on a kamado, such as the Big Green Egg, Kamado Joe and Primo, has become the ultimate way to enjoy delicious dishes outdoors. Thanks to the versatility of the kamado, this can be done all year round, regardless of the weather. Authors Jeroen Hazebroek and Leonard Elenbaas, experts in the field of kamados, share their extensive knowledge and experience in their book 'Hete Kolen Compleet'. With more than 40,000 copies sold, this is the standard work for every kamado enthusiast.