This optional chamber mimics the passive preinfusion you find on the venerable E61 group head. Instead of all the pump pressure flowing straight through the group head, the pre-infusion chamber diverts some of the flow resulting in a gradual 6-second ramp to full pressure. This saturates the coffee bed more gently to minimize channeling, making even extractions easier and shots more consistent! 

This chamber is compatible with the  and the .  Installing the chamber is both easy and reversible.