The Prep works by progressive fresh guacamole ProKeeper is the perfect solution for keeping guacamole fresh for longer periods of time. The press fit seal protects guacamole from air and prevents browning. You simply press the lid down into the container to expel the excess air. The base container is also perfect for both storing and serving guacamole. Progressive Pro tip: form a mound in the middle of the keeper before pressing the lid all the way down. Doing this helps to ensure a tight seal.