Barista Basics Knockbox (6" Round) The Barista Basics Knockbox made with ultra-strong ABS plastic and include a removable NBR rubber knock bar. Each unit is packaged with an oversized NBR rubber hush gasket for added resilience and noise reduction. The removable knock bar and sleek ABS design make these units easy to clean. BPA free Designed for in-counter application Includes NBR rubber hush gasket, removable NBR rubber knock bar, and NBR rubber base Holds up to 25+ discarded pucks 5mm thick, durable ABS plastic NBR rubber and ABS plastic combine for reduced impact noise