The dual-sided tamper compresses ground espresso into a densely compacted, evenly dispersed puck. The pressurized water then flows more slowly for the richest, most robust extraction possible. It also creates a necessary gap between the top of the grounds and the water disbursement screen so the dampened grounds don't swell to clog the water flow for a silty mess. Dual ends (48mm and 53mm) fit most portafilter baskets and the 4-ounce weight assists in the tamping process for an effortless preparation. Made from heavyweight aluminum, it endures the naturally occurring acids found in coffee.