All professional espresso tampers, from all manufacturers, are 58mm in diameter. It’s the chosen standard for all commercial espresso machines and most home ones. While a number of good espresso machines uses other size portafilters (and thus tampers), it’s generally a good size to see 58mm equipment.
If you are in the market for a 58mm espresso tamper, we are here to help. The cafe world has settled on 58mm tampers as being the standard, which means there are a huge number of options, but navigating those options can be a challenge.