If you are looking for the ideal fabric for winter socks, you do not need to look further. Merino wool, is originated in the 13th century in the Spanish kingdom. A sheep breed was created from a cross between sheep from the Middle East and North Africa. Merinos was considered a national treasure, in the 18th century, the royal government introduced a strict ban on the export of these valuable animals outside the state and disobedience was punished by death. This wool, until today, is an ideal fabric with excellent insulating -isothermal in fact- properties, but its breathable as well, as it is one of the quickest drying natural fabrics, while at the same time the quality of the fiber is such that it does not trap smells like a synthetic fabric. Ingeniously, Castelli mixes the merino fiber with the synthetic but biodegradable PrimaLoft® so that the resulting fabric has the magical properties of Merino but with the elasticity and longevity of a synthetic. A national treasure at your feet, then, for all seasons, for cold or heat, with Alpha 18, which means with a height of 18 cm.