About This Knock Box Opening Diameter of 10cm/3.9in - Perfect for 49/51/54/58mm espresso portafilters. Knock the portafilter against the knock bar for quick, easy and mess-free disposal of the espresso coffee puck. Knock Box for Espresso Coffee Grounds Capacity - Pefect espresso accessories for store about 10pcs espresso pucks, for quick and easy disposal. Small size espresso puck knock box for home coffee bar used. Premium Material - Durable ABS coffee knock box body with textured stainless steel housing, upgraded stainless steel knock bar with silicone sleeve, reduce knocking noise and protect your portafilter. Luxe Outllook Design - Perfect for storing next to your espresso machine on the counter, 12.8cm/5in tall allow to store on the espresso drip tray when not in use. Professional Coffee Grounds Knock Box Design - With anti-slip rubber base, stable and reduce noise when knocking out espresso puck, protect your countertop without scratches. Detachable knock bar design for easy to empty and clean.