A bottomless portafilter by La Cimbali.
The portafilter originally started out as a spouted portafilter. Included with the portafilter 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.
The La Cimbali Bottomless Portafilter fits almost all of the Cimbali machines, including the Junior Casa.
NOTE: This does not fit the lever-action piston Cimbali.