A flat base. While companies have tried to sell buyers on the virtues of convex tamper bases, there is no evidence (anecdotal or tested) that supports the use of convex bases. Flat base tampers are the default and the ones used by almost all professional and home baristas. While experimenting with tampers and tamping technique is a good idea, the single most important quality of a tamp is the amount of pressure and that's all the vast majority of