The Tamper

Tamper: the device used to tamp a bed of loose, finely ground coffee in a portafilter, in preparation for brewing espresso. Most espresso machines include a plastic tamper as an accessory, and after market tampers can be bought. They are measured in millimeter sizes, corresponding with the filter basket internal diameter of your espresso machine. Most commercial, prosumer, and high end consumer espresso machines use a 58mm tamper; other common sizes are 49mm, 53mm, and 57mm.