The Caran d’Ache Museum Aquarelle and Holbein Watercolor pencils are similar aesthetically speaking, both pencils sporting hexagonal barrels with the Holbein barrel weighing in at 7.4mm and the Caran d’Ache barrel slightly bigger at 7.6mm. The cores of both pencils are approximately 4.1mm, a hugely generous core given the quality of pigments held within each core.