Unlike the big scouring pads you might have in your kitchen, these are made to fit into your portafilter (see photo)! They are 58 mm. wide.
When you clean your equipment, its important to scrub out the portafilter basket using soap and a good scouring pad. Oils from the coffee tend to accumulate in the tiny holes at the bottom of the filter basket, where it will obstruct future extractions, and make your shots bitter.
So when you clean your equipment at the end of the day, you should scrub out the portafilter with soap and water, and get the oils out of the filter grid using this 58 mm. wide scouring pad.
The large scouring pads in your kitchen will not (easily) let you get into the corners of your filter-basket. These sponges are made to fit. Further, if you use these exclusively for your portafilters, they will not accumulate other kitchen grime that you don't want in your coffee.
These scouring pads are 3.5" long (the large dimension), 58 mm. wide (the small dimension - about 2.3"), and 3/4" thick. Comes as a set of three.