The Rocket Espresso Water Reservoir Filter will bring crisp, clean water with the right amount of minerals to extract a tasty espresso shot. This filter is quick and easy to install. Just moisten the filter with cold water 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. After installing, leave the filter in the machine until it needs to be replaced (the filter typically last from 6-12 months depending on usage).