A rocks glass, also known as an old-fashioned glass, is a short, sturdy glass typically used for serving spirits or cocktails. It usually has a wide mouth and a heavy base, making it ideal for drinks served on the rocks, meaning over ice. The design allows for easy mixing and muddling of ingredients, which is common in cocktails like the Old Fashioned. Rocks glasses generally hold between 6 to 10 ounces of liquid. They are often made from glass or crystal and can come in various styles and designs. This versatile glass is popular in bars and homes for serving both neat spirits and mixed drinks.