Staresso Dosing Ring 53mm for SP300 STARESSO Dosing Ring/Coffee Funnel 53mm for Mirage SP300 The dosing ring design to made doing your coffee less mess. This is particularly useful with a doserless grinder, when trying to direct the grinder output into your portafilter. It’s basically a mini-funnel that sits on top of your portafilter basket. Model no: F6 Material: Aluminium Alloy Dosing Ring diameter: 53mm