Portafilter

A portafilter is the handled fitting that holds the metal filter basket containing your ground coffee, and it locks into the espresso machine's group head so pressurized hot water can pass through. Portafilters come in different sizes, commonly 54, 58, and 58.4 millimeters, and baskets are matched to that size and to a specific dose range.

Bottomless, or naked, portafilters remove the spouts and show the coffee stream directly as it exits, which makes problems like channeling and uneven distribution immediately visible instead of hidden inside the spouts. This makes them a popular tool for dialing in technique, though they can spray if the puck is prepped poorly.

When choosing a portafilter, match it to your machine's group head size and check whether it fits both regular and bottomless baskets. A common mistake is using a basket sized for a much smaller or larger dose than you actually use, which makes even, consistent tamping and distribution difficult no matter how careful your technique is.