Doppio

Doppio espresso is a double shot, extracted using a double coffee filter in the portafilter.[1] This results in 60 ml of drink, double the amount of a single shot espresso. More commonly called a standard double, it is a standard in judging the espresso quality in barista competitions but only because four single espresso are made using two double portafilters. Doppio is Italian multiplier, meaning "double"

Extracting a doppio

A single shot of espresso, by contrast, is called a solo ("single") and developed because it was the maximum amount that could practically be extracted on lever espresso machines. Today (but only outside italy) the Doppio is the standard shot, and because solos require a different filter basket, solo shots are often produced by making ("pulling") a doppio in a two-spout portafilter, but only catching one of the streams (the other stream may be discarded or used in another drink).