Bottomless Portafilters This bottomless portafilter or naked portafilter fits to the espresso machines. It fits with the 3 shot 21g filter. It helps to control and diagnose extraction of espresso shots and assures a pure espresso with a great crema. Its a amazing espresso accessory for training, because channeling will show you, that the coffee ground is not properly compressed, or it just garanties a perfect show.