E61 Group Bottomless Portafilter An ergonomically designed bottomless portafilter by Rancilio. The Bottomless Portafilter for the Rancilio Silvia comes with Rancilio "RR" logo and comes directly from the manufacturer. Included with the Bottomless Portafilter for the Rancilio Silvia is a standard triple insert basket. What is a bottomless portafilter and what is it used for? Bottomless portafilters are used as a training tool. It will provide you with immediate feedback and can see if channeling occurs right away. Channeling is the rapid passage of water through fractures in the coffee puck, which produces a thinner, under-extracted espresso. When it occurs, you'll often see sudden appearances of blond streaks in the stream of espresso; sometimes the puck will even have pencil lead-sized holes where channeling occurred. Weight: 1.05 lbs Insert basket: 21 grams The Rancilio Erogonomic Bottomless Portafilter fits all of the Rancilio commercial machines, the Silvia, as well as other E61 group machines. Some examples include: Quick Mill Andreja Premium, Anita, Vetrano, Alexia and Silvano. Izzo Alex and Alex Duetto- Isomac Millenium, Tea, Rituale, Relax, Zaffiro, and Amica. Expobar Office Control, Office Pulser, Office Lever, and Brewtus. ECM Giotto, Cellini, Rocket, and Giotto Premium - Grimac and Grimac Valentina.