Overview The Nuova Simonelli Bottomless Portafilter, originally a spouted portafilter, includes a double insert basket and is compatible with commercial machines like the Aurelia, Appia, Oscar, and Musica. As a training tool, bottomless portafilters provide immediate feedback and allow you to monitor for potential issues such as channeling. This occurs when water rapidly passes through fractures in the coffee puck, resulting in a thin and under-extracted espresso. By using a bottomless portafilter, you can easily spot these issues and make necessary adjustments.