What size tamper should I use for the ROK espresso maker?

For ROK and Presso espresso makers, we recommend a 49.7mm tamper. This is the maximum size which will allow the tamper to fit neatly past the ridge inside the portafilter basket. A larger tamper will be obstructed by the ridge, preventing effective tamping. At a minimum, you can use a 49mm tamper but we don’t recommend anything smaller than that.