This Bottomless (Naked) Portafilter is designed to suit Rancilio Silvia espresso machines. It comes with a 3 shot 21g filter basket. Bottomless Portafilters are great as the filter basket is exposed so you can see the whole extraction process and diagnose any problems with the shot. They are also an excellent tool for training as channeling and colour can indicate an uneven tamp or incorrect grinder setting. One thing is for sure, the Bottomless (Naked) Portafilter guaranties an awesome show while extracting espresso shots.