I Want the Pinot Grigio

Guardian Unlimited Special reports Vineyard in a box becomes the must-have gift for Italian townies: "Not everyone in Italy owns a vineyard in Chianti. Most people live in cramped apartments in cities such as Rome and Naples where the idea of harvesting grapes has, until now, been an unattainable dream. But no longer: this year's essential Christmas present for urban Italians is a miniature vineyard that can be planted in a window box or grown on the smallest balcony.
Paolo Roiatti, who runs a garden centre near Udine in northern Italy, came up with the idea after experimenting with planting vines in confined spaces."
What would such a tiny vineyard yield? A glass or two?