Pondmaster® 12315 Small Pond Pump Filter Bag, 18" x 24"Goes over the entire pump system in the bottom of your pond to keep the larger debris from clogging your pump & filter system. Can be used in skimmers or independently as a mechanical pre filter in open pond applications. Tear and clog resistant. 18" x 24" Small Goes over the entire pump system in the bottom of your pond to keep the larger debris from clogging your pump & filter system Can be used in skimmers or independently as a mechanical pre