Portafilter Ring (Funnel?) for Rancilio Silvia

I built this to stop the coffee grounds from spilling out over the top of my portafilter when I grind coffee into it. It's designed for a Rancilio Silvia espresso maker but you should be able to resize it to fit almost any basket. It works surprisingly well.

EDIT: I re-printed this after upgrading my printer and found that the fit was a bit tight. To fix it I put the portafilter basket in the oven (200C ish) and then pushed the ring into it. Perfect fit.