Measuring cups are used in cooking to measure accurate portion sizes of liquid and dry ingredients in recipes. Most are made from metal, glass, or plastic and use the standard 8 ounce (236.5 ml) "cup" as the basic unit of measurement. If measurements are made in US or imperial measurements (cups, teaspoons, etc.), then it is important to use the proper cups when dealing with both dry and liquid ingredient lists. A cup of flour is not measured in the same way as a cup of vegetable oil is, so cooks usually keep two sets on hand. Dry measurements are usually made in plastic or metal containers, while liquids may be measured in transparent glass or plastic cups.