The most important thing about your tamper is that it has the right diameter for your espresso machines, the tamper should not be too small, but certainly not too tight. In the latter case, the tamper remains clamped in the filter. The tamper is therefore usually a fraction smaller than the stated size. In addition, there are tampers with a flat and a conical bottom. There is something to be said for both applications. Flat ensures that the water can distribute evenly over the coffee and conical adapts more to the shape of the shower of your coffee machine.