I just got my first machine, and I'm looking to replace the flimsy plastic tamper that came with the Gaggia Classic. It seems like the two common tamper sizes are 50mm and 55mm, but the 55mm I tried from a friend was still too small. Any idea what the proper size tamper is?
Actually the most common and widely used basket/tamper size is the 58mm. It also seemed, from a quick Google, that the Gaggia Classic does indeed use a 58mm portafilter basket so you'll want to find a 58mm tamper for it.