Replacement Filter Mat for Savio Skimmerfilter, Set of 4 (1-year Supply) Replacement Filter Mat Designed for use with Savio Skimmerfilter Pond Filtration Systems Mats measure approximately 17" x 13-3/4" x 1" This 1-year supply is a great value for keeping your pond clean. This is a package of 4 filters - It is recommended that along with regular cleanings, you replace the filter every 3 months. These are made to work with the full size Skimmerfilter, and are not compatible with the Compact Skimmerfilter. Please double-check the measurements carefully.