Dreamfarm Grindenstein Knock Box espresso knock box give you ample storage space for holding the residual coffee grounds so that you can later transfer them to a compost bin. Rubberized knock bar won’t dent or scratch your portafilter and helps eliminate spills, it keeps The Portafilter Safe. The puck box features a non-slip rubber pad on the bottom to stabilize the knock box and reduce noise, prevents sliding and won’t scratch kitchen countertops.