With the Rocket Espresso Water Reservoir Filter, you'll have crisp, clean water with the right amount of minerals to extract a tasty espresso shot. Installation involves moistening the filter and placing it in the water tank. This handy filter will work with almost any espresso machine or coffee maker with a reservoir. Besides providing optimal water quality users will notice a reduction in scale buildup. Update: Rockets suggests changing the filter every 2 months. Be sure to set a reminder!