The funnel-shaped ring from Rhino Coffee Gear is designed for 57-58 mm portafilters to minimize the spillage of ground coffee outside the portafilter. It helps keep your brewing area tidy and efficient. With the Dosing Funnel, you can be sure that your coffee dose will hit its target in your portafilter. Around it, 4 magnets securely lock the ring onto your machine's portafilter.