Designed to fit baskets of 58mm diameter, they're fully compatible with many of the E61, Flair 58, ECM, Rocket, Sanremo, Synesso, Slayer, VBM, etc. Espresso Machine models. A bottomless portafilter is an important piece of equipment that aids in diagnosing espresso extraction issues. The spouts are removed, the basket is exposed, allowing you to watch the entire extraction process. The Bottomless Portafilter sometimes referred to as a Naked Portafilter has become an essential addition to any quality-orientated espresso shop's barista tools. Our bottomless portafilters are made from 304 stainless steel and an Anodized Aluminum handle. PLEASE NOTE: Channeling and spurting can be very messy, but are EXTREMELY common. This is not a defect of the portafilter itself, but instead, is your coffee telling you that there's room for improvement in your preparation process (grind size, tamping, distribution, etc.)