The designs of ‘O’ are based on the benchmark shapes of Riedel Vinum. For the first time in glass history the design parameters such as shape of tumbler, size and diameter of rim, have been finely-tuned to enhance the world's most important grape varietals. ‘O’ is available as: Cabernet/Merlot, Pinot/Nebbiolo, Syrah/Shiraz, Chardonnay, Viognier/Chardonnay, Riesling/Sauvignon.