Blind Shaker Espresso Coffee Dosing Cup, designed to fit from 48mm to 58mm portafilters. Not dishwasher safe. The way you use it is by Dosing directly into the cup with the plunger in place. Then, put the cup over the portafilter, remove the lid, and then pull out the plunger releasing the grounds in to the portafilter basket.
eBay