Portafilter machines share certain common elements with professional machines used in the hotel and restaurant industry. These include a removable sieve that is filled with coffee grounds and attached to the machine with a bayonet mount system. Some portafilter machines do not have a built-in grinder; therefore, a coffee grinder needs to be bought separately if freshly ground coffee is desired. By using a coffee grinder, the user can influence numerous factors that have an impact on quality. These include: the degree of grinding, the amount and compression applied to the coffee grounds placed in the sieve as well as brewing time. With a bit of practice, this process can be perfected to suit the type of coffee that is being used and to achieve better results than a fully automatic coffee machine.