1. 54mm Naked/Bottomless Portafilter-54mm portafilter head was designed to be compatible with Breville the Barista Express, Barista Pro, Barista Touch, Bambino Plus, Infuser and Duo-Temp Pro. 2. Extraction Improvement- Use a 54mm bottomless portafilter to really see what's happening under the hood, you can identify and correct extraction problems, whether your grind is wrong or you are tamping incorrectly the bottomless portafilter will let you know. A great tool for beginners and experts. 3. Ergonomic Design- Portafilter handle is made of natural sandalwood, solid surface and ergonomic design to ensure perfect grip and easy manual control; Portafilter head is cast in food grade stainless steel and high polished by manual, precise size ensures portafilter engaged in the group firmly. 4. IMPORTANT NOTE - Our portafilters are designed to fit snug into the espresso machine group head, providing a tight seal when brewing. However, due to the varying tolerances between machines, some may fit more snug than other. In the rare case that you experience fitment issues, please reach out to our team directly.