The length of the shot can be "ristretto" (or "stretto") (reduced), "normale" or standard (normal), or "lungo" (long): these may correspond to a smaller or larger drink with the same amount of ground coffee and same level of extraction or to different length of extraction. Proportions vary and the volume (and low density) of crema make volume-based comparisons difficult (precise measurement uses the mass of the drink). Typically "ristretto" is half the volume of "normale", and "lungo" is double to triple the "normale" volume. For a double shot, (14 grams of dry coffee), a "normale" uses about 60 ml of water. A "double ristretto," a common form associated with espresso, uses half the amount of water, about 30 ml.