Sailor Soul Stackable Wine Glass - Set of 6 The stackable wine glass of Sailor Soul Collection is made of Ecozen, a new high-end material, probably the best for the manufacture of synthetic glassware, ultra resistant to shocks and with a crystal appearance. It is dishwasher and microwave safe with high durability, without the appearance of scratches or opacity. In addition, when using this material in outdoor areas we avoid possible accidents with glass breakage.