Mixing Glass, 14 oz., DuraTuff, (Top diameter 3.50", bottom diameter 2.375"). Libbey With innovation as its cornerstone, Libbey Mixing Glass. quality, consistency, and exceptional customer service have become the standard in the industry. Libbey continues to invest in state-of-the-art production equipment and faster and more efficient manufacturing technologies, allowing it to create the most significant introductions in the foodservice and consumer markets.