Having trouble finding a 51mm funnel for my expresso machine (Delonghi EC685) filter holder, I designed mine :
It has the particularity of plugging perfectly into the filter holder, it even holds its head upside down! It is important in order not to spill the coffee everywhere in case of bad action (note: the size is adjusted for non-pressurized filte, you will have to force a little more for pressurized filte sold with the machine because the diameter must be 0.2mm larger).
the height allows to contain a large volume of grind and allows to pass easily under the nozzle of the coffee grinder.
it is simple and elegant because it is important for a barista ^^