 The wine is a blend of 30-45% Croatina, 25-40% Barbera, 5-15% Uva Rara and up to 15% of other local red grape varieties to round out the blend.All grapes destined for DOC wine production need to be harvested to a yield no greater than 11 tonnes/ha.The finished wine must attain a minimum alcohol level of 11% in order to be labelled with the San Colombano DOC designation.