Grinding straight into the portafilter is neat until half the grounds end up on the counter and around the rim. This dosing funnel fixes that. It sits on top of your basket and its raised walls funnel every bit of coffee into the basket instead of over the sides, so nothing spills and the rim stays clean for a proper seal. The extra height also gives you room to distribute and level a full dose without it overflowing. It won't improve your extraction on its own, that's down to how you distribute and tamp, but it keeps the whole station tidy. It comes in 51, 53, and 58 mm, in silver or black, so pick the size that matches your basket, and just wipe it clean.